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❓A teacher is making packed lunches for a field trip. Each student needs 2 sandwiches, and will travel in a group with a certain number of other students. There are a total of 5 groups. The teacher needs 120 pieces of bread to make enough sandwiches for all the students. How many students are in each group, excluding the student themselves?
💡First, I need to determine the total number of students going on the field trip. Each student requires 2 sandwiches, and each sandwich uses 2 pieces of bread. By dividing the total number of bread pieces by 2, I can find the total number of sandwiches needed:120 pieces of bread ÷ 2 = 60 sandwiches.Since each student needs 2 sandwiches, I divide the total number of sandwiches by 2 to find the total number of students:60 sandwiches ÷ 2 = 30 students.There are 5 groups in total. To find out how many students are in each group, I divide the total number of students by the number of groups:30 students ÷ 5 groups = 6 students per group.Finally, to determine the number of students in each group excluding the student themselves, I subtract 1 from the total number of students in each group:6 students per group - 1 student = 5 students.
❓In the rectangular coordinate system (xOy), point M has polar coordinates left(2, frac{2π}{3}right). Convert these polar coordinates to rectangular coordinates.A: left(-1, sqrt{3}right)B: left( sqrt{3},-1right)C: left(- sqrt{3},1right)D: left(1,- sqrt{3}right)
💡To convert the polar coordinates ((2, frac{2pi}{3})) to rectangular coordinates, we use the conversion formulas:[x = r cos theta][y = r sin theta]Here, (r = 2) and (theta = frac{2pi}{3}).First, calculate (x):[x = 2 cos left(frac{2pi}{3}right)]The cosine of (frac{2pi}{3}) is (-frac{1}{2}), so:[x = 2 times left(-frac{1}{2}right) = -1]Next, calculate (y):[y = 2 sin left(frac{2pi}{3}right)]The sine of (frac{2pi}{3}) is (frac{sqrt{3}}{2}), so:[y = 2 times frac{sqrt{3}}{2} = sqrt{3}]Therefore, the rectangular coordinates are ((-1, sqrt{3})).
❓Let ( Q(x) ) be a polynomial such that[ Q(x) = Q(0) + Q(1) x + Q(3) x^2 ]and ( Q(-2) = 2. ) Find ( Q(x). )
💡Okay, so I have this problem where I need to find a polynomial Q(x) such that it's expressed as Q(0) + Q(1)x + Q(3)x², and also Q(-2) equals 2. Hmm, that seems a bit tricky, but let me try to break it down step by step.First, I know that Q(x) is a polynomial, and it's given in a specific form: Q(0) + Q(1)x + Q(3)x². That means Q(x) is a quadratic polynomial because the highest power of x is 2. So, Q(x) should look like ax² + bx + c, right? But in this case, the coefficients are given in terms of Q evaluated at specific points: Q(0), Q(1), and Q(3). Interesting.Let me write down what I know:1. Q(x) = Q(0) + Q(1)x + Q(3)x²2. Q(-2) = 2So, my goal is to find the coefficients Q(0), Q(1), and Q(3), which will allow me to write down Q(x) explicitly.Let me denote Q(0) as a, Q(1) as b, and Q(3) as c for simplicity. So, Q(x) = a + bx + cx².Now, since Q(x) is a quadratic polynomial, I can express it as Q(x) = cx² + bx + a, where a, b, c are constants. But in the problem, it's given as Q(0) + Q(1)x + Q(3)x², so that aligns with my notation.Now, I need to find a, b, and c. I have one equation from Q(-2) = 2, but I also can get more equations by evaluating Q(x) at x=0, x=1, and x=3 because those are the points where the coefficients are defined.Let me write down these evaluations:1. Q(0) = a2. Q(1) = a + b + c3. Q(3) = a + 3b + 9cBut wait, from the problem statement, Q(x) is given as a + bx + cx², so when I plug in x=1, I get Q(1) = a + b + c, and when I plug in x=3, I get Q(3) = a + 3b + 9c.But from the problem, Q(1) is just b, and Q(3) is just c. Wait, that doesn't make sense. Let me think again.Wait, no, in the problem, Q(x) is expressed as Q(0) + Q(1)x + Q(3)x². So, in my notation, that would be a + bx + cx², where a = Q(0), b = Q(1), and c = Q(3). So, when I plug in x=1, Q(1) should equal a + b + c, but according to the problem, Q(1) is just b. So, that gives me an equation: a + b + c = b. Similarly, when I plug in x=3, Q(3) should equal a + 3b + 9c, but according to the problem, Q(3) is just c. So, that gives another equation: a + 3b + 9c = c.So, now I have two equations:1. a + b + c = b2. a + 3b + 9c = cLet me simplify these equations.From the first equation: a + b + c = b. Subtract b from both sides: a + c = 0. So, a = -c.From the second equation: a + 3b + 9c = c. Subtract c from both sides: a + 3b + 8c = 0.But since a = -c, I can substitute a in the second equation: (-c) + 3b + 8c = 0. Simplify: 7c + 3b = 0. So, 3b = -7c, which means b = (-7/3)c.Now, I also have the condition that Q(-2) = 2. Let's plug x = -2 into Q(x):Q(-2) = a + b*(-2) + c*(-2)² = a - 2b + 4c = 2.But we already have a = -c and b = (-7/3)c. Let's substitute these into the equation:(-c) - 2*(-7/3)c + 4c = 2.Simplify each term:- c + (14/3)c + 4c = 2.Let me convert all terms to have a common denominator of 3:(-3/3)c + (14/3)c + (12/3)c = 2.Combine the terms:(-3 + 14 + 12)/3 c = 2.Calculate the numerator: -3 + 14 = 11, 11 + 12 = 23.So, (23/3)c = 2.Solve for c:c = 2 * (3/23) = 6/23.Now, since a = -c, a = -6/23.And b = (-7/3)c = (-7/3)*(6/23) = (-42)/69 = (-14)/23.So, now I have a = -6/23, b = -14/23, and c = 6/23.Therefore, Q(x) = a + bx + cx² = (-6/23) + (-14/23)x + (6/23)x².I can factor out 1/23 to make it look cleaner:Q(x) = (6x² -14x -6)/23.Let me double-check my work to make sure I didn't make any mistakes.First, check the equations:1. a + c = 0: (-6/23) + (6/23) = 0. Correct.2. 3b + 7c = 0: 3*(-14/23) + 7*(6/23) = (-42/23) + (42/23) = 0. Correct.3. Q(-2) = (-6/23) -2*(-14/23) +4*(6/23) = (-6/23) + (28/23) + (24/23) = ( (-6 +28 +24)/23 ) = (46/23) = 2. Correct.Everything checks out. So, the polynomial Q(x) is (6x² -14x -6)/23.I can also write it as Q(x) = (6x² -14x -6)/23, which simplifies to Q(x) = (6x² -14x -6)/23.Alternatively, I can factor out a 2 from the numerator:Q(x) = 2*(3x² -7x -3)/23 = (6x² -14x -6)/23.Either way is correct, but I think the first form is fine.So, the final answer is Q(x) = (6x² -14x -6)/23.
❓Write sqrt{frac{16}{25} + frac{9}{4} + frac{1}{16}} as a common fraction.
💡Okay, so I have this problem here: I need to find the square root of the sum of three fractions, specifically sqrt(16/25 + 9/4 + 1/16), and express it as a common fraction. Hmm, let me think about how to approach this step by step.First, I know that to add fractions, they need to have the same denominator. So, I need to find a common denominator for 16/25, 9/4, and 1/16. Let's see, the denominators are 25, 4, and 16. I need to find the least common denominator (LCD) for these numbers. Breaking them down:- 25 is 5 squared, so its prime factors are 5 and 5.- 4 is 2 squared, so its prime factors are 2 and 2.- 16 is 2 to the fourth power, so its prime factors are 2, 2, 2, and 2.To find the LCD, I take the highest power of each prime number present in the factorizations. So, for 2, the highest power is 2^4 (from 16), and for 5, it's 5^2 (from 25). Therefore, the LCD is 16 * 25, which is 400. Okay, so 400 is the common denominator.Now, I need to convert each fraction to have 400 as the denominator.Starting with 16/25:- To get from 25 to 400, I multiply by 16 (since 25 * 16 = 400).- So, I multiply both the numerator and denominator by 16: (16 * 16)/(25 * 16) = 256/400.Next, 9/4:- To get from 4 to 400, I multiply by 100 (since 4 * 100 = 400).- So, I multiply both the numerator and denominator by 100: (9 * 100)/(4 * 100) = 900/400.Lastly, 1/16:- To get from 16 to 400, I multiply by 25 (since 16 * 25 = 400).- So, I multiply both the numerator and denominator by 25: (1 * 25)/(16 * 25) = 25/400.Now, I can rewrite the original expression with these equivalent fractions:sqrt(256/400 + 900/400 + 25/400).Since all the denominators are the same, I can add the numerators:256 + 900 + 25 = 1181.So, the expression simplifies to sqrt(1181/400).Now, I need to simplify sqrt(1181/400). I can separate the square root of the numerator and the denominator:sqrt(1181)/sqrt(400).I know that sqrt(400) is 20 because 20 * 20 = 400. So, this becomes sqrt(1181)/20.Now, I need to check if sqrt(1181) can be simplified further. To do this, I'll see if 1181 is a perfect square or if it has any square factors.Let me try dividing 1181 by some small prime numbers to see if it's divisible:- 1181 ÷ 2 = 590.5 → Not an integer.- 1181 ÷ 3 ≈ 393.666 → Not an integer.- 1181 ÷ 5 = 236.2 → Not an integer.- 1181 ÷ 7 ≈ 168.714 → Not an integer.- 1181 ÷ 11 ≈ 107.364 → Not an integer.- 1181 ÷ 13 ≈ 90.846 → Not an integer.- 1181 ÷ 17 ≈ 69.47 → Not an integer.- 1181 ÷ 19 ≈ 62.158 → Not an integer.- 1181 ÷ 23 ≈ 51.348 → Not an integer.- 1181 ÷ 29 ≈ 40.724 → Not an integer.- 1181 ÷ 31 ≈ 38.097 → Not an integer.Since none of these divisions result in an integer, it seems like 1181 doesn't have any square factors other than 1. Therefore, sqrt(1181) cannot be simplified further.So, putting it all together, the expression sqrt(16/25 + 9/4 + 1/16) simplifies to sqrt(1181)/20.I think that's as simplified as it gets. So, the final answer is sqrt(1181) over 20.
❓A man owns 1/3 of a market research bureau business and sells 3/5 of his shares for 15,000 rs. What is the value of the business?
💡First, I need to determine the value of the man's total shares before he sold any portion of them. He sold 3/5 of his shares for ₹15,000. By setting up the equation (3/5) * V = 15,000, where V represents the total value of his shares, I can solve for V.Next, I'll calculate V by dividing ₹15,000 by 3/5, which simplifies to multiplying by 5/3. This gives me the total value of the man's shares before the sale.Once I have the value of the man's total shares, I recognize that this amount represents 1/3 of the entire business. To find the total value of the business, I'll set up another equation where 1/3 of the business's total value equals the value of the man's shares. By multiplying the value of the man's shares by 3, I can determine the total value of the business.Finally, after performing the calculations, I'll present the total value of the market research bureau business.
❓All candies of different varieties available in the warehouse are sorted into n boxes, each box priced at 1, 2, ..., n. a) Which boxes should be bought when n=10 and k=3?b) The same question for any natural numbers n geq k.
💡Alright, so I've got this problem about candies in boxes, and I need to figure out which boxes to buy when there are 10 boxes and I want to buy 3 of them. Then, I also need to generalize this for any number of boxes and any number of boxes to buy, as long as the number of boxes is at least the number of boxes I want to buy. Hmm, okay, let me try to break this down.First, the problem says that all candies of different varieties are sorted into n boxes, each priced at 1, 2, ..., n. So, each box has a unique price, starting from 1 up to n. In part a, n is 10 and k is 3, so I need to figure out which 3 boxes to buy out of 10. In part b, it's for any natural numbers n ≥ k.I think the key here is to maximize the total value or something, but the problem doesn't specify exactly what we're trying to maximize. Wait, actually, the problem doesn't mention anything about maximizing or minimizing, just "which boxes should be bought." Maybe it's about selecting boxes in such a way that the average price is maximized or something like that? Or perhaps it's about ensuring that the selection is spread out in some way.Looking at the initial problem statement again, it says "all candies of different varieties available in the warehouse are sorted into n boxes, each box priced at 1, 2, ..., n." So, each box has a unique price, and the prices are consecutive integers starting from 1. So, the boxes are priced at 1, 2, 3, ..., up to n.Now, the question is, which boxes should be bought when n=10 and k=3? And then generalize it for any n ≥ k.Wait, maybe it's about selecting k boxes such that their prices are as high as possible? Or perhaps it's about selecting boxes in such a way that the total price is maximized? Or maybe it's about selecting boxes that are spread out in terms of their prices?Wait, let me think. If I have 10 boxes priced from 1 to 10, and I need to buy 3 of them, which ones should I choose? If I want to maximize the total price, I should choose the most expensive ones, which would be boxes 8, 9, and 10. But maybe that's not the case. Alternatively, if I want to spread out my selection, maybe I should choose every third box or something like that.Wait, actually, the problem might be related to the concept of selecting a subset of boxes such that the average price of the selected boxes is as high as possible, or perhaps it's about ensuring that the selection is representative of the entire range of prices.Alternatively, maybe it's about selecting boxes in such a way that the sum of their prices is maximized, which would again point towards choosing the most expensive ones. But I'm not sure if that's the case.Wait, let me think again. The problem says "all candies of different varieties available in the warehouse are sorted into n boxes, each box priced at 1, 2, ..., n." So, each box has a unique price, and the prices are consecutive integers. So, the boxes are priced at 1, 2, 3, ..., n.Now, the question is, which boxes should be bought when n=10 and k=3? And then generalize it for any n ≥ k.Wait, maybe it's about selecting k boxes such that their prices are as high as possible, but also ensuring that they are spread out in some way. For example, if I choose the three most expensive boxes, 8, 9, and 10, that might be too clustered at the high end. Alternatively, if I choose boxes 4, 7, and 10, that spreads them out more evenly across the price range.Wait, actually, I think this might be related to the concept of selecting a subset of elements such that their average is maximized, but also ensuring that the subset is as spread out as possible. Or perhaps it's about selecting boxes in such a way that the sum of their prices is maximized, but also ensuring that they are spread out.Wait, let me think about the general case first. If I have n boxes and I need to choose k of them, how should I choose them? Maybe it's about selecting every (n/k)th box or something like that. For example, if n=10 and k=3, then n/k is approximately 3.333, so maybe selecting boxes at positions 4, 7, and 10? Because 10/3 is about 3.333, so the first box would be at 4, the next at 7, and the last at 10.Wait, that seems plausible. Let me test this idea. If I have 10 boxes, and I want to choose 3, then dividing 10 by 3 gives approximately 3.333. So, starting from the first box, I would take every 4th box? Wait, no, that would be 1, 5, 9. But that's only 3 boxes, but 10/3 is about 3.333, so maybe it's better to distribute the selection more evenly.Alternatively, maybe it's about selecting the boxes such that the difference between consecutive selected boxes is as uniform as possible. So, for 10 boxes and selecting 3, the spacing between selected boxes would be roughly 10/3 ≈ 3.333. So, starting from box 1, the next would be box 5, then box 9. But that leaves out box 10, which is the most expensive.Alternatively, maybe starting from the end. If I want to select the most expensive boxes, but also spread them out, I could select box 10, then box 7, then box 4. That way, I'm selecting every 3rd box from the end, which gives me 4, 7, and 10. That seems to spread them out more evenly across the price range.Wait, let me think about why 4, 7, and 10. If I divide 10 into 3 equal parts, each part is about 3.333. So, starting from the beginning, the first third would end at box 3.333, so the next box would be 4. Then, the next third would end at 6.666, so the next box would be 7. Then, the last third would end at 10. So, selecting boxes at positions 4, 7, and 10.Yes, that makes sense. So, for n=10 and k=3, the boxes to buy would be 4, 7, and 10.Now, for the general case, when n ≥ k, how would this selection work? It seems like we're dividing the n boxes into k equal segments, and selecting the box at the end of each segment. So, the first segment would be from box 1 to box n/k, the second segment from n/k + 1 to 2n/k, and so on, until the kth segment. Then, we select the last box of each segment.But since n and k are integers, n/k might not be an integer, so we need to take the ceiling or floor of n/k to determine the exact positions. So, in general, the boxes to buy would be at positions ceil(n/k), ceil(2n/k), ..., ceil(kn/k). But since kn/k is n, the last box is always n.Wait, let me test this with n=10 and k=3. n/k is approximately 3.333, so ceil(10/3) is 4, ceil(20/3) is 7, and ceil(30/3) is 10. So, that gives us boxes 4, 7, and 10, which matches our earlier selection.So, in general, for any n ≥ k, the boxes to buy would be at positions ceil(n/k), ceil(2n/k), ..., ceil(kn/k). Since ceil(kn/k) is just n, that's the last box.But wait, let me think about another example to make sure this works. Suppose n=7 and k=3. Then, n/k is approximately 2.333. So, ceil(7/3)=3, ceil(14/3)=5, and ceil(21/3)=7. So, the boxes to buy would be 3, 5, and 7. Let's see if that makes sense. Dividing 7 boxes into 3 segments, each segment is about 2.333 boxes. So, the first segment ends at box 3, the second at box 5, and the third at box 7. That seems reasonable.Another example: n=6, k=2. n/k=3, so ceil(6/2)=3, ceil(12/2)=6. So, boxes 3 and 6. That makes sense, as dividing 6 boxes into 2 segments of 3 each, selecting the last box of each segment.Wait, but what if n is not divisible by k? Let's say n=5, k=2. n/k=2.5, so ceil(5/2)=3, ceil(10/2)=5. So, boxes 3 and 5. That seems correct, as dividing 5 boxes into 2 segments, the first segment ends at box 3, the second at box 5.Okay, so it seems like the general formula is to select the boxes at positions ceil(jn/k) for j=1,2,...,k. So, for each j from 1 to k, compute ceil(jn/k) and select the box at that position.But wait, let me think about why this works. If we want to spread out the selection as evenly as possible across the n boxes, dividing the boxes into k equal segments and selecting the last box of each segment ensures that the selected boxes are as evenly spaced as possible. This maximizes the minimum distance between selected boxes, which is a common approach in problems where you want to spread out selections.Alternatively, if we were to select the boxes in a way that the sum of their prices is maximized, we would just select the k most expensive boxes, which would be n, n-1, ..., n-k+1. But that's different from what we're doing here.So, in this problem, it seems like the goal is to select k boxes such that they are as spread out as possible across the entire range of box prices. Therefore, the optimal selection would be to divide the n boxes into k equal segments and select the last box of each segment.Therefore, for n=10 and k=3, the boxes to buy are 4, 7, and 10. For the general case, the boxes to buy are at positions ceil(jn/k) for j=1,2,...,k.Wait, but let me double-check this with another example. Suppose n=8, k=3. Then, n/k≈2.666. So, ceil(8/3)=3, ceil(16/3)=6, ceil(24/3)=8. So, boxes 3, 6, and 8. Let's see if that's the most spread out selection. The segments would be 1-3, 4-6, and 7-8. So, selecting the last box of each segment, which are 3, 6, and 8. That seems reasonable.Alternatively, if we were to select every 3rd box starting from 1, we'd get 1,4,7. But that's only 3 boxes, and 7 is less than 8, so maybe 1,4,7 is another possible selection. But according to our formula, it's 3,6,8. Which one is better?Well, if we're trying to spread out the selection as much as possible, 3,6,8 might be better because 8 is the most expensive box, and 3 and 6 are spread out in the lower and middle ranges. Whereas 1,4,7 might leave out the most expensive box.Wait, but in the problem statement, it's not specified whether we want to include the most expensive box or not. It just says "which boxes should be bought." So, maybe it's about maximizing the total price, in which case including the most expensive box would be better. But our formula includes the most expensive box, so that seems better.Alternatively, if we were to select boxes such that the average price is maximized, then including the most expensive boxes would be better. But if we're selecting them to be spread out, then maybe including the most expensive box is still better because it's the highest value.Wait, I think the key here is that the problem is about selecting k boxes such that their prices are as high as possible while also being spread out. So, including the most expensive box is important, but also ensuring that the other selected boxes are spread out in the lower and middle ranges.Therefore, the formula of selecting ceil(jn/k) for j=1,2,...,k seems to achieve that balance. It ensures that we're selecting the most expensive box, and also selecting boxes that are spread out in the lower and middle ranges.So, in conclusion, for part a) when n=10 and k=3, the boxes to buy are 4, 7, and 10. For part b), for any natural numbers n ≥ k, the boxes to buy are at positions ceil(jn/k) for j=1,2,...,k.Wait, but let me think about the exact formula. Is it ceil(jn/k) or floor((j-1)n/k) +1? Because sometimes when dividing into segments, you have to be careful about how you index them.Let me think about n=10, k=3. j=1: ceil(10/3)=4, j=2: ceil(20/3)=7, j=3: ceil(30/3)=10. So, that works.For n=7, k=3: j=1: ceil(7/3)=3, j=2: ceil(14/3)=5, j=3: ceil(21/3)=7. That works too.For n=5, k=2: j=1: ceil(5/2)=3, j=2: ceil(10/2)=5. That works.So, it seems like the formula ceil(jn/k) works for selecting the boxes.Alternatively, another way to think about it is that each segment has a length of approximately n/k, so the first segment is from 1 to ceil(n/k), the second from ceil(n/k)+1 to ceil(2n/k), and so on. Then, the last box of each segment is selected.Yes, that makes sense. So, the formula is consistent.Therefore, I think I've got it. For part a), the boxes to buy are 4, 7, and 10. For part b), the boxes to buy are at positions ceil(jn/k) for j=1,2,...,k.