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question:Calculate the value of the following expressions:(I) 0.064,^{- frac {1}{3}}-(- frac {4}{5})^{0}+0.01,^{ frac {1}{2}};(II) 2lg 5+lg 4+ln sqrt {e}.
answer:Alright, so I have these two expressions to calculate. Let me take them one at a time and see if I can figure them out. I'm a bit nervous because exponents and logarithms can be tricky, but I'll give it a shot.Starting with the first expression: (0.064,^{- frac {1}{3}} - (- frac {4}{5})^{0} + 0.01,^{ frac {1}{2}}). Hmm, okay, let's break this down term by term.First term: (0.064,^{- frac {1}{3}}). Negative exponents mean reciprocals, right? So this should be the same as (frac{1}{0.064^{frac{1}{3}}}). Now, (0.064) looks familiar. I think it's a cube of something. Let me check: (0.4 times 0.4 times 0.4 = 0.064). Yes, that's right! So (0.064^{frac{1}{3}} = 0.4). Therefore, (frac{1}{0.4}) is the same as (2.5). Okay, so the first term simplifies to (2.5).Second term: (-(- frac {4}{5})^{0}). Wait, any non-zero number to the power of 0 is 1, right? So ((- frac {4}{5})^{0} = 1). But there's a negative sign in front, so it becomes (-1). Got it.Third term: (0.01,^{ frac {1}{2}}). This is the square root of 0.01. I know that (0.1 times 0.1 = 0.01), so the square root of 0.01 is 0.1. Easy enough.Now, putting it all together: (2.5 - 1 + 0.1). Let's compute that. (2.5 - 1 = 1.5), and (1.5 + 0.1 = 1.6). So, the first expression simplifies to 1.6. I think 1.6 can be written as a fraction, which is (frac{8}{5}). Yeah, that makes sense.Alright, moving on to the second expression: (2lg 5 + lg 4 + ln sqrt {e}). Okay, logarithms. I need to remember the properties of logarithms here.First term: (2lg 5). That's straightforward; it's just twice the logarithm base 10 of 5. I know that (lg 5) is approximately 0.69897, but maybe I can keep it symbolic for now.Second term: (lg 4). Hmm, 4 is (2^2), so using the logarithm power rule, (lg 4 = lg 2^2 = 2lg 2). That might be useful later.Third term: (ln sqrt {e}). Square root is the same as raising to the power of (frac{1}{2}), so (ln e^{frac{1}{2}}). Using the logarithm power rule again, this becomes (frac{1}{2} ln e). And since (ln e = 1), this simplifies to (frac{1}{2}).So, putting it all together: (2lg 5 + 2lg 2 + frac{1}{2}). Wait a minute, (2lg 5 + 2lg 2) can be factored. Let me see: (2(lg 5 + lg 2)). And (lg 5 + lg 2 = lg (5 times 2) = lg 10). Since (lg 10 = 1), this simplifies to (2 times 1 = 2). So now, the entire expression is (2 + frac{1}{2} = 2.5). Which is the same as (frac{5}{2}).Let me double-check my steps to make sure I didn't make any mistakes. For the first expression, I converted the negative exponent correctly, recognized the cube root of 0.064 as 0.4, and handled the negative sign in the second term properly. The square root of 0.01 was straightforward. Adding them up gave me 1.6, which is indeed (frac{8}{5}).For the second expression, I used logarithm properties correctly. Breaking down (lg 4) into (2lg 2) was smart because it allowed me to combine terms later. Recognizing that (lg 5 + lg 2 = lg 10 = 1) was key, and then adding (frac{1}{2}) to 2 gave me the final result of (frac{5}{2}). I think I did this correctly.Just to be thorough, I'll plug in the approximate values for the logarithms in the second expression. (lg 5 approx 0.69897) and (lg 2 approx 0.30103). So, (2lg 5 approx 2 times 0.69897 = 1.39794), and (2lg 2 approx 2 times 0.30103 = 0.60206). Adding these together: (1.39794 + 0.60206 = 2). Then adding (frac{1}{2}) gives (2 + 0.5 = 2.5), which confirms my earlier result. So, I'm confident that both expressions are correctly simplified.**Final Answer**(I) (boxed{dfrac{8}{5}})(II) (boxed{dfrac{5}{2}})
question:Given the equation a + 2b = 32, where |a| > 2, and a and b are both integers. The smallest possible value of a that can be used to solve the equation is 4. What is the value of b when a is at its smallest possible value?
answer:Okay, so I have this equation: a + 2b = 32. And there are some conditions: |a| > 2, which means that the absolute value of a is greater than 2. Also, both a and b have to be integers. The problem says that the smallest possible value of a is 4, and I need to find the value of b when a is at its smallest possible value.First, I need to understand what |a| > 2 means. Absolute value of a being greater than 2 means that a can't be -2, -1, 0, 1, or 2. So, a has to be less than or equal to -3 or greater than or equal to 3. But the problem says the smallest possible value of a is 4. Wait, that seems a bit confusing because if a can be as low as -3, why is the smallest possible value 4? Maybe I'm misunderstanding something.Let me read the problem again: "Given the equation a + 2b = 32, where |a| > 2, and a and b are both integers. The smallest possible value of a that can be used to solve the equation is 4. What is the value of b when a is at its smallest possible value?"Hmm, so maybe the smallest possible value of a in the context of solving the equation is 4. That is, even though a could theoretically be as low as -3, in the context of this equation, the smallest a that still allows b to be an integer is 4. So, I need to find b when a is 4.Alright, let's substitute a = 4 into the equation:4 + 2b = 32Now, I need to solve for b. Subtract 4 from both sides:2b = 32 - 42b = 28Then, divide both sides by 2:b = 28 / 2b = 14So, when a is 4, b is 14.Wait, but just to make sure I'm not missing anything, let me check if there's a smaller a that still satisfies |a| > 2 and makes b an integer. The problem says the smallest possible a is 4, but maybe I should verify that.Let's try a = 3. Then:3 + 2b = 322b = 29b = 14.5But b has to be an integer, so 14.5 isn't allowed. So, a = 3 doesn't work.What about a = 2? But |a| > 2, so a can't be 2. Similarly, a = 1, 0, -1, -2 are all excluded because of |a| > 2.What about a = -3? Let's try that:-3 + 2b = 322b = 35b = 17.5Again, not an integer. So, a = -3 doesn't work either.How about a = -4?-4 + 2b = 322b = 36b = 18That's an integer. So, a = -4 gives b = 18. But wait, the problem says the smallest possible value of a is 4. But here, a = -4 is smaller than 4, and it works. So, maybe I'm misunderstanding the problem.Is there something I'm missing? Maybe the problem is referring to the smallest positive value of a, not the smallest overall. If that's the case, then a = 4 is indeed the smallest positive integer greater than 2 that satisfies the equation with b being an integer.But the problem doesn't specify positive or negative, just the smallest possible value. So, if a can be negative, then a = -4 is smaller than 4, and it works. So, why does the problem say the smallest possible value of a is 4?Maybe there's a constraint I'm not considering. Let me check the original problem again."Given the equation a + 2b = 32, where |a| > 2, and a and b are both integers. The smallest possible value of a that can be used to solve the equation is 4. What is the value of b when a is at its smallest possible value?"Hmm, it says the smallest possible value of a is 4. So, perhaps in the context of the problem, a is being considered as a positive integer, or maybe there's another constraint I'm not seeing.Alternatively, maybe the problem is implying that a is positive because it's referring to the smallest possible value in the positive direction. If that's the case, then a = 4 is indeed the smallest positive integer greater than 2 that satisfies the equation with b being an integer.But to be thorough, let's consider both possibilities.If a can be negative, then a = -4 is smaller than 4, and it works. So, why does the problem say the smallest possible value is 4? Maybe there's a misinterpretation.Alternatively, perhaps the problem is referring to the smallest positive value of a, not the overall smallest. In that case, a = 4 is correct.Given that the problem states the smallest possible value of a is 4, I think it's safe to proceed with a = 4 and find b accordingly.So, substituting a = 4:4 + 2b = 322b = 28b = 14Therefore, when a is at its smallest possible value of 4, b is 14.But just to be absolutely sure, let me try a = 5:5 + 2b = 322b = 27b = 13.5Not an integer. So, a = 5 doesn't work.a = 6:6 + 2b = 322b = 26b = 13That's an integer. So, a = 6 works, but since a = 4 is smaller, 4 is the smallest possible a.Wait, but earlier I found that a = -4 works as well. So, unless there's a constraint that a must be positive, a = -4 is smaller than 4.But the problem says the smallest possible value of a is 4, so maybe it's considering positive integers only. Therefore, a = 4 is the smallest positive integer greater than 2 that satisfies the equation with b being an integer.In conclusion, when a is 4, b is 14.
question:There are 14240 books in a library. They are arranged on shelves that hold a certain number of books each. There are 1780 shelves in the library. How many books does each shelf hold?
answer:First, I need to determine how many books each shelf holds by dividing the total number of books by the total number of shelves.The total number of books is 14,240, and there are 1,780 shelves.So, I will calculate 14,240 divided by 1,780.Performing the division:14,240 ÷ 1,780 = 8Therefore, each shelf holds 8 books.
question:What is the minimum number of equilateral triangles, each with a side length of 2 units, required to completely cover an equilateral triangle with a side length of 16 units?
answer:Okay, so I have this problem where I need to figure out the minimum number of small equilateral triangles, each with a side length of 2 units, required to completely cover a larger equilateral triangle with a side length of 16 units. Hmm, let me think about how to approach this.First, I know that both the small and large triangles are equilateral, which means all their sides are equal, and all their angles are 60 degrees. That should help because the shapes are similar, so their areas should be proportional to the square of their side lengths. Maybe I can use the area to figure out how many small triangles fit into the large one.Let me recall the formula for the area of an equilateral triangle. I think it's something like (sqrt(3)/4) multiplied by the side length squared. So, for the small triangle with side length 2 units, the area would be:A_small = (sqrt(3)/4) * (2)^2 = (sqrt(3)/4) * 4 = sqrt(3) square units.Okay, that seems right. Now, for the large triangle with side length 16 units, the area would be:A_large = (sqrt(3)/4) * (16)^2 = (sqrt(3)/4) * 256 = 64 * sqrt(3) square units.So, if I divide the area of the large triangle by the area of the small triangle, I should get the number of small triangles needed to cover the large one, right?Number of small triangles = A_large / A_small = (64 * sqrt(3)) / sqrt(3) = 64.Wait, so does that mean I need 64 small triangles to cover the large one? That seems straightforward, but I'm not sure if it's that simple. Maybe there's something I'm missing here.I remember that when covering shapes, especially with smaller shapes, sometimes you have to consider how they fit together and if there's any overlap or gaps. In this case, since both triangles are equilateral and similar, maybe they can fit perfectly without any gaps or overlaps. So, perhaps 64 is actually the correct number.But let me visualize this. If I have a large equilateral triangle and I want to cover it with smaller equilateral triangles, each of side length 2 units, how would they fit? The large triangle has a side length of 16 units, so along one side, how many small triangles would fit?If each small triangle has a side length of 2 units, then along the side of the large triangle, which is 16 units, I can fit 16 / 2 = 8 small triangles. So, along each side of the large triangle, there are 8 small triangles.Now, in an equilateral triangle, the number of small triangles along each side corresponds to the number of rows in the larger triangle. So, if there are 8 small triangles along the base, there would be 8 rows of small triangles in the large triangle.To find the total number of small triangles, I can use the formula for the sum of the first n natural numbers, which is n(n + 1)/2. Here, n is 8, so:Total small triangles = 8 * (8 + 1)/2 = 8 * 9 / 2 = 72 / 2 = 36.Wait, that's different from the 64 I calculated earlier using areas. Hmm, so which one is correct?I think the confusion arises because when I calculated using areas, I assumed that the small triangles can perfectly tile the large triangle without any gaps or overlaps, which might not be the case if we're just placing them side by side. But when I think about it in terms of rows, I'm considering how many small triangles fit along each side and then summing them up.But why is there a discrepancy between the two methods? Let me double-check my calculations.First, the area method:A_small = sqrt(3) square units.A_large = 64 * sqrt(3) square units.Number of small triangles = 64 * sqrt(3) / sqrt(3) = 64.That seems correct.Now, the row method:Number of small triangles along one side = 16 / 2 = 8.Total number of small triangles = 8 * (8 + 1)/2 = 36.Wait, 36 is much less than 64. That doesn't make sense because the area method suggests that 64 small triangles are needed.I think the issue here is that in the row method, I'm assuming that the small triangles are arranged in a way that they form a larger equilateral triangle, but in reality, to cover the entire area, you might need more triangles because of the way they overlap or fit together.Alternatively, maybe the row method is not the right approach here because it's more suited for counting the number of small triangles that can fit perfectly within the large triangle without overlapping, but in reality, to cover the entire area, you might need more triangles.Let me think differently. If I consider the ratio of the side lengths, the large triangle is 16 units, and the small triangles are 2 units. So, the ratio is 16:2, which simplifies to 8:1. This means that along each side of the large triangle, there are 8 small triangles.In terms of area, since area scales with the square of the side length, the ratio of areas would be (8)^2 = 64. So, the area of the large triangle is 64 times the area of the small triangle, which means you need 64 small triangles to cover the large one.That makes sense. So, the area method gives me 64, which seems to be the correct answer.But why did the row method give me 36? Maybe because the row method is counting the number of small triangles that can fit perfectly within the large triangle without overlapping, but in reality, to cover the entire area, you need more triangles because you have to account for the overlapping areas or the way the triangles are arranged.Alternatively, perhaps the row method is not the right approach for this problem. Maybe it's better to stick with the area method since it directly relates the areas and gives a clear answer.So, based on the area calculation, I need 64 small triangles to cover the large one.But just to be thorough, let me think about how the small triangles would actually be arranged to cover the large one. If I have a large equilateral triangle, and I want to cover it with smaller equilateral triangles, each of side length 2 units, how would that look?I can imagine dividing the large triangle into smaller triangles by drawing lines parallel to the sides. Each side of the large triangle is 16 units, so if I divide each side into segments of 2 units, I'll have 8 segments per side.Then, by drawing lines parallel to the sides at each 2-unit interval, I can create a grid of smaller equilateral triangles within the large one. Each of these smaller triangles would have a side length of 2 units.In this case, the number of small triangles would be the same as the number of small triangles along one side squared, which is 8^2 = 64. So, that aligns with the area method.Therefore, it seems that both methods, when correctly applied, give me the same answer of 64 small triangles needed to cover the large one.I think I was confused earlier because I was misapplying the row method, not considering that the number of rows corresponds to the number of small triangles along one side, and the total number of small triangles is actually the square of that number.So, in conclusion, the minimum number of small equilateral triangles needed to cover the large one is 64.
question:Among the following analogical reasoning conclusions, the correct one is ( )A: "If a cdot 3 = b cdot 3, then a = b" analogically leads to "If a cdot 0 = b cdot 0, then a = b"B: "If (a + b)c = ac + bc" analogically leads to "(a cdot b)c = ac cdot bc"C: "If (a + b)c = ac + bc" analogically leads to "frac{a + b}{c} = frac{a}{c} + frac{b}{c} (c neq 0)"D: "(ab)^n = a^n b^n" analogically leads to "(a + b)^n = a^n + b^n"
answer:Alright, so I've got this multiple-choice question about analogical reasoning in mathematics. It's asking which of the given analogical conclusions is correct. The options are labeled A, B, C, and D. Let me try to understand each one step by step.First, I need to recall what analogical reasoning means. From what I remember, analogical reasoning involves drawing conclusions by comparing two things that are alike in some ways. In mathematics, this often means applying a property or rule from one situation to another similar situation. However, it's crucial to ensure that the analogy holds true and doesn't lead to incorrect conclusions.Let's look at each option one by one.**Option A:**"If ( a cdot 3 = b cdot 3 ), then ( a = b )" analogically leads to "If ( a cdot 0 = b cdot 0 ), then ( a = b )."Okay, so the first statement is about multiplying by 3. If two numbers multiplied by 3 give the same result, then the original numbers must be equal. That makes sense because multiplication by a non-zero number is reversible; you can divide both sides by 3 to get ( a = b ).But the analogy here is to multiply by 0 instead. So, if ( a cdot 0 = b cdot 0 ), does that mean ( a = b )? Hmm, multiplying any number by 0 gives 0, right? So both sides would be 0 regardless of the values of ( a ) and ( b ). That means ( a ) and ( b ) could be any numbers, and the equation would still hold. Therefore, this analogy doesn't hold because you can't conclude ( a = b ) from ( a cdot 0 = b cdot 0 ). So, Option A is incorrect.**Option B:**"If ( (a + b)c = ac + bc )" analogically leads to "( (a cdot b)c = ac cdot bc )."Alright, the first part is the distributive property of multiplication over addition. It's a fundamental property in algebra, stating that multiplying a sum by a number is the same as multiplying each addend by the number and then adding the results. That makes sense.Now, the analogy is to apply a similar property to multiplication instead of addition. So, instead of distributing multiplication over addition, we're trying to distribute multiplication over multiplication. The statement becomes ( (a cdot b)c = ac cdot bc ). Let's test this with some numbers to see if it holds.Let me choose ( a = 2 ), ( b = 3 ), and ( c = 4 ).Left-hand side (LHS): ( (2 cdot 3) cdot 4 = 6 cdot 4 = 24 ).Right-hand side (RHS): ( 2 cdot 4 cdot 3 cdot 4 = 8 cdot 12 = 96 ).Clearly, 24 ≠ 96. So, this analogy doesn't hold either. Therefore, Option B is incorrect.**Option C:**"If ( (a + b)c = ac + bc )" analogically leads to "( frac{a + b}{c} = frac{a}{c} + frac{b}{c} ) ( (c neq 0) )."Here, the original statement is again the distributive property of multiplication over addition. The analogy is to apply a similar property to division instead of multiplication. So, instead of distributing multiplication over addition, we're distributing division over addition.Let me see if this works. The statement says that dividing the sum of ( a ) and ( b ) by ( c ) is the same as dividing each term separately and then adding the results. That is, ( frac{a + b}{c} = frac{a}{c} + frac{b}{c} ).Let's test this with some numbers. Let ( a = 4 ), ( b = 6 ), and ( c = 2 ).Left-hand side (LHS): ( frac{4 + 6}{2} = frac{10}{2} = 5 ).Right-hand side (RHS): ( frac{4}{2} + frac{6}{2} = 2 + 3 = 5 ).They are equal in this case. Let me try another set to be sure. Let ( a = 5 ), ( b = 3 ), and ( c = 1 ).LHS: ( frac{5 + 3}{1} = frac{8}{1} = 8 ).RHS: ( frac{5}{1} + frac{3}{1} = 5 + 3 = 8 ).Again, they are equal. It seems like this analogy holds true. So, Option C is correct.**Option D:**"( (ab)^n = a^n b^n )" analogically leads to "( (a + b)^n = a^n + b^n )."Alright, the original statement is about the exponentiation of a product. It's a standard property that when you raise a product to a power, it's the same as raising each factor to that power and then multiplying the results. So, ( (ab)^n = a^n b^n ) is correct.Now, the analogy is to apply this property to a sum instead of a product. So, instead of ( (ab)^n ), we have ( (a + b)^n ), and instead of ( a^n b^n ), we have ( a^n + b^n ). The statement becomes ( (a + b)^n = a^n + b^n ).Let me test this with some numbers to see if it's true. Let's choose ( a = 1 ), ( b = 1 ), and ( n = 2 ).Left-hand side (LHS): ( (1 + 1)^2 = 2^2 = 4 ).Right-hand side (RHS): ( 1^2 + 1^2 = 1 + 1 = 2 ).Clearly, 4 ≠ 2. So, this analogy doesn't hold. Therefore, Option D is incorrect.**Conclusion:**After analyzing each option, only Option C holds true under analogical reasoning. The others either lead to incorrect conclusions or don't maintain the properties required for the analogy to be valid.
question:Without using a calculator, find the largest prime factor of 18^4 + 2 times 18^2 + 1 - 16^4.
answer:Okay, so I need to find the largest prime factor of this expression: (18^4 + 2 times 18^2 + 1 - 16^4). Hmm, that looks a bit complicated, but maybe I can simplify it somehow. Let me write it down again to see if I can spot a pattern or a way to factor it.First, let me look at the expression: (18^4 + 2 times 18^2 + 1 - 16^4). I notice that the first three terms, (18^4 + 2 times 18^2 + 1), look similar to a quadratic in terms of (18^2). Let me set (x = 18^2) to make it easier. Then the expression becomes (x^2 + 2x + 1 - 16^4). Wait, (x^2 + 2x + 1) is a perfect square. It factors into ((x + 1)^2). So substituting back, that part becomes ((18^2 + 1)^2). So now the entire expression is ((18^2 + 1)^2 - 16^4). Hmm, that looks like a difference of squares because (16^4) is ((16^2)^2). So I can factor this as ((18^2 + 1 - 16^2)(18^2 + 1 + 16^2)). Let me compute each part separately.First, compute (18^2). I know that (18^2 = 324). Then, (16^2 = 256). So plugging these into the first factor: (324 + 1 - 256). That simplifies to (325 - 256 = 69). Now, the second factor is (324 + 1 + 256). Adding those together: (324 + 1 = 325), and (325 + 256 = 581). So now, the original expression simplifies to (69 times 581).Okay, so now I need to factor both 69 and 581 to find their prime factors. Starting with 69: I know that 69 divided by 3 is 23, because 3 times 23 is 69. So, 69 factors into 3 and 23, both of which are prime numbers.Now, moving on to 581. This one is a bit trickier. Let me check if it's divisible by smaller primes. First, check divisibility by 2: 581 is odd, so no. Next, check 3: 5 + 8 + 1 = 14, which isn't divisible by 3, so no. Next, check 5: it doesn't end with 0 or 5, so no. Then, 7: Let's see, 7 times 83 is 581? Wait, 7 times 80 is 560, and 7 times 3 is 21, so 560 + 21 = 581. So, 581 divided by 7 is 83. Wait, is 83 a prime number? Let me check. 83 is not divisible by 2, 3, 5, 7, or 11. The square root of 83 is a little over 9, so I only need to check primes up to 9. Since none of them divide 83, it is indeed a prime number. So, 581 factors into 7 and 83.Putting it all together, the original expression factors into (3 times 23 times 7 times 83). Now, looking at these prime factors: 3, 7, 23, and 83. The largest one among these is 83. Wait, hold on, earlier I thought 581 was 11 times 53, but now I'm getting 7 times 83. Did I make a mistake? Let me double-check. 7 times 83 is indeed 581 because 7 times 80 is 560, plus 7 times 3 is 21, so 560 + 21 = 581. So, 581 is 7 times 83, and both are primes. Therefore, the prime factors are 3, 7, 23, and 83. So, the largest prime factor is 83.Wait, but earlier I thought it was 53. Hmm, maybe I confused it with another problem. Let me confirm. 581 divided by 7 is 83, which is prime. So, 83 is the larger prime factor here. Therefore, the largest prime factor of the original expression is 83.But wait, in my initial calculation, I thought 581 was 11 times 53, but that must have been a mistake. Let me check 11 times 53: 11 times 50 is 550, plus 11 times 3 is 33, so 550 + 33 = 583, which is actually 583, not 581. So, that was incorrect. Therefore, 581 is indeed 7 times 83, and 83 is prime.So, going back, the prime factors are 3, 7, 23, and 83. So, the largest prime factor is 83.Wait, but in the initial problem, the user wrote the expression as (18^4 + 2 times 18^2 + 1 - 16^4), which I simplified to ((18^2 + 1)^2 - (16^2)^2), then factored into ((18^2 + 1 - 16^2)(18^2 + 1 + 16^2)), which gave me 69 and 581. Then factoring those, I got 3, 23, 7, and 83. So, the largest prime factor is 83.But in the initial assistant's response, it was stated as 53. So, perhaps there was a miscalculation there. Let me make sure I didn't make a mistake in my calculations.Wait, 18^2 is 324, 16^2 is 256. So, 324 + 1 - 256 is 69, and 324 + 1 + 256 is 581. Then, 69 is 3 times 23, and 581 is 7 times 83. So, the prime factors are 3, 23, 7, and 83. So, the largest is 83.Therefore, I think the initial assistant's response had an error in factoring 581 as 11 times 53, which is incorrect because 11 times 53 is 583, not 581. So, the correct largest prime factor is 83.Wait, but let me double-check 581 divided by 7: 7 times 80 is 560, 581 minus 560 is 21, which is 7 times 3, so yes, 7 times 83 is 581. And 83 is a prime number. So, yes, 83 is the correct largest prime factor.Therefore, the largest prime factor of the given expression is 83.