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question:Solve for ordered pairs (m, n) of positive integers such that [ frac{5}{m} + frac{3}{n} = 1 text{ and } m text{ is an odd number.} ] A) 0 B) 1 C) 2 D) 3 E) More than 3
answer:1. Start with the given equation: [ frac{5}{m} + frac{3}{n} = 1. ] 2. Multiply both sides by mn: [ 5n + 3m = mn. ] 3. Rearrange the terms: [ mn - 5n - 3m = 0. ] 4. Add 15 to both sides to aid with factoring: [ mn - 5n - 3m + 15 = 15. ] [ (m-3)(n-5) = 15. ] 5. Factorize 15 to find integer pairs that satisfy (m-3, n-5): [ 15 = 1 times 15, 15 = 3 times 5, 15 = 15 times 1, 15 = -1 times -15, 15 = -3 times -5, 15 = -15 times -1. ] Positive pairs are: [ (m-3, n-5) = (1, 15), (3, 5), (15, 1). ] And translating back to (m, n) gives: [ (m, n) = (4, 20), (6, 10), (18, 6). ] 6. Apply the condition that m must be odd: [ (m, n) = (4, 20), (6, 10), (18, 6) Rightarrow text{None of these have } m text{ as odd, so no solutions.} ] Conclusion: The condition that m is odd yields no valid pairs, thus there are 0 solutions. The final answer is boxed{A) 0}
question:A smooth ball with a radius of 1 cm was dipped in red paint and set between two absolutely smooth concentric spheres with radii of 4 cm and 6 cm, respectively (the ball is outside the smaller sphere but inside the larger one). Upon contact with both spheres, the ball leaves a red mark. During its movement, the ball traveled along a closed path, resulting in a region on the smaller sphere outlined in red with an area of 37 square centimeters. Find the area of the region outlined in red on the larger sphere. Give your answer in square centimeters, rounding to the nearest hundredth if necessary.
answer:1. **Identify the given and required areas**: - Given: The radius of the smaller sphere ( r_1 = 4 ) cm. - Given: The radius of the larger sphere ( r_2 = 6 ) cm. - The area on the smaller sphere marked by the ball is ( 37 ) square cm. 2. **Understand the ratio of the spherical caps on the two spheres**: - The spherical caps left by the ball on both the smaller and larger spheres will have a proportional area based on the square of their respective radii. This is derived from the fact that for a given spherical cap created by an object maintaining its curvature, the area of the cap is proportional to the square of the radius of the sphere (( A propto r^2 )). 3. **Calculate the proportionality ratio**: - Since area ( A propto r^2 ), the ratio of the areas on the two spheres due to the same spherical cap is: [ frac{A_2}{A_1} = frac{r_2^2}{r_1^2} = frac{6^2}{4^2} = frac{36}{16} = frac{9}{4} ] 4. **Determine the area on the larger sphere**: - Let ( A_2 ) represent the area on the larger sphere. - By the ratio derived, ( A_2 = A_1 times frac{9}{4} ). - Substitute ( A_1 = 37 ) square cm: [ A_2 = 37 times frac{9}{4} = 37 times 2.25 = 83.25 ] **Conclusion**: [ boxed{83.25} ]
question:Determine ( k ) such that the expression [ a x^{2} + b x + c + k left( x^{2} + 1 right) ] is a perfect square. Show that ( k ) has two real values.
answer:To determine the value(s) of ( k ) such that the expression [ a x^{2}+b x+c+kleft(x^{2}+1right) ] is a perfect square, we need to manipulate the expression and set conditions for it to be a perfect square trinomial. 1. **Rewrite the expression**: [ a x^{2}+b x+c+k(x^{2}+1) ] Simplifies to: [ (a+k)x^{2} + b x + (c+k) ] 2. **Condition for a perfect square**: For the quadratic expression ((a+k)x^{2} + b x + (c+k)) to be a perfect square, it must be of the form: [ left( sqrt{a+k} x + sqrt{c+k} right)^2 ] When expanded, the squared form becomes: [ left( sqrt{a+k} x + sqrt{c+k} right)^2 = (sqrt{a+k})^2 x^2 + 2 sqrt{a+k} sqrt{c+k} x + (sqrt{c+k})^2 ] which simplifies to: [ (a+k) x^2 + 2 sqrt{(a+k)(c+k)} x + (c+k) ] By comparing coefficients, we see that: [ b = 2 sqrt{(a+k)(c+k)} ] 3. **Solving for ( k )**: Square both sides of the above equation: [ b^2 = 4(a+k)(c+k) ] 4. **Formulate and solve the quadratic equation in ( k )**: Rewrite the equation as: [ b^2 = 4ac + 4ak + 4ck + 4k^2 ] Move all terms to one side: [ 4k^2 + 4(a+c)k + 4ac - b^2 = 0 ] Divide the entire equation by 4: [ k^2 + (a+c)k + ac - frac{b^2}{4} = 0 ] 5. **Solve the quadratic equation using the quadratic formula**: The quadratic formula is: [ k = frac{-B pm sqrt{B^2 - 4AC}}{2A} ] Here, ( A = 1 ), ( B = a+c ), and ( C = ac - frac{b^2}{4} ): [ k = frac{-(a+c) pm sqrt{(a+c)^2 - 4 (ac - frac{b^2}{4})}}{2} ] 6. **Simplify the discriminant**: [ k = frac{-(a+c) pm sqrt{(a+c)^2 - 4ac + b^2 }}{2} ] Notice that: ((a+c)^2 - 4ac = a^2 + c^2 + 2ac - 4ac = a^2 + c^2 - 2ac = (a-c)^2) Hence: [ k = frac{-(a+c) pm sqrt{(a-c)^2 + b^2}}{2} ] 7. **Final values for ( k )**: [ k = frac{-(a+c) + sqrt{(a-c)^2 + b^2}}{2} ] and [ k = frac{-(a+c) - sqrt{(a-c)^2 + b^2}}{2} ] 8. **Conclusion**: Since (sqrt{(a-c)^2 + b^2}) is always a real number (non-negative), ( k ) has two real values. Therefore, ( k ) has indeed two real values. [boxed{k = -frac{a+c}{2} pm frac{1}{2} sqrt{(a-c)^2 + b^2}}]
question:m of rs . 2795 is lent into two parts so that the interest on the first part for 8 years at 3 % per annum may be equal to the interest on the second part for 3 years at 5 % per annum . find the second sum ?
answer:Let the first part of the sum be x rupees and the second part be (2795 - x) rupees. According to the problem, the interest on the first part for 8 years at 3% per annum is equal to the interest on the second part for 3 years at 5% per annum. Interest on the first part = Principal × Rate × Time / 100 Interest on the first part = x × 3% × 8 / 100 Interest on the first part = x × 3 × 8 / 100 Interest on the first part = 24x / 100 Interest on the second part = Principal × Rate × Time / 100 Interest on the second part = (2795 - x) × 5% × 3 / 100 Interest on the second part = (2795 - x) × 5 × 3 / 100 Interest on the second part = (2795 - x) × 15 / 100 Since the interests are equal, we can set them equal to each other: 24x / 100 = (2795 - x) × 15 / 100 Now, we can solve for x: 24x = (2795 - x) × 15 24x = 41925 - 15x 24x + 15x = 41925 39x = 41925 x = 41925 / 39 x = 1075 So, the first part of the sum is 1075 rupees. Now, we can find the second part of the sum: Second part = Total sum - First part Second part = 2795 - 1075 Second part = 1720 Therefore, the second sum is boxed{1720} rupees.