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If the A.M. and G.M. between two numbers...

If the A.M. and G.M. between two numbers are respectively 17 and 8, find the numbers.

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To find the two numbers given that their Arithmetic Mean (A.M.) is 17 and their Geometric Mean (G.M.) is 8, we can follow these steps: ### Step 1: Set up the equations for A.M. and G.M. The formulas for the A.M. and G.M. of two numbers \( a \) and \( b \) are given by: \[ \text{A.M.} = \frac{a + b}{2} \] \[ \text{G.M.} = \sqrt{ab} \] From the problem, we know: \[ \frac{a + b}{2} = 17 \] \[ \sqrt{ab} = 8 \] ### Step 2: Solve for \( a + b \) using A.M. From the A.M. equation: \[ a + b = 2 \times 17 = 34 \] ### Step 3: Solve for \( ab \) using G.M. From the G.M. equation: \[ ab = 8^2 = 64 \] ### Step 4: Substitute \( b \) in terms of \( a \) Using the equation \( a + b = 34 \), we can express \( b \) in terms of \( a \): \[ b = 34 - a \] ### Step 5: Substitute \( b \) in the product equation Now substitute \( b \) into the product equation \( ab = 64 \): \[ a(34 - a) = 64 \] Expanding this gives: \[ 34a - a^2 = 64 \] ### Step 6: Rearrange the equation Rearranging the equation: \[ -a^2 + 34a - 64 = 0 \] Multiplying through by -1 to make the leading coefficient positive: \[ a^2 - 34a + 64 = 0 \] ### Step 7: Solve the quadratic equation Now we can use the quadratic formula to solve for \( a \): \[ a = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] Here, \( a = 1, b = -34, c = 64 \): \[ a = \frac{34 \pm \sqrt{(-34)^2 - 4 \cdot 1 \cdot 64}}{2 \cdot 1} \] Calculating the discriminant: \[ = \frac{34 \pm \sqrt{1156 - 256}}{2} \] \[ = \frac{34 \pm \sqrt{900}}{2} \] \[ = \frac{34 \pm 30}{2} \] This gives us two possible values for \( a \): 1. \( a = \frac{64}{2} = 32 \) 2. \( a = \frac{4}{2} = 2 \) ### Step 8: Find corresponding values for \( b \) Using \( b = 34 - a \): 1. If \( a = 32 \), then \( b = 34 - 32 = 2 \). 2. If \( a = 2 \), then \( b = 34 - 2 = 32 \). ### Conclusion The two numbers are \( 2 \) and \( 32 \). ---
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ICSE-SEQUENCE AND SERIES -EXERCISE 14 (e)
  1. Find: (i) the 7th term of 2,4,8,... (ii) the 9th term of 1,(1)/(2),(1)...

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  2. The second term of a G.P. is 18 and the fifth term is 486. Find: (i)...

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  3. Find the value of x for which x +9,x-6, 4 are the first three terms of...

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  4. If 5, x, y, z, 405 are the first five terms of a geometric progression...

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  5. Insert 3 geometric means between 16 and 256.

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  6. Insert 5 geometric means between (1)/(3) and 243.

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  7. If the A.M. and G.M. between two numbers are respectively 17 and 8, fi...

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  8. The second, third and sixth terms of an A.P. are consecutive terms of ...

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  9. The 5th, 8th and 11th terms of a G.P. are P, Q and S respectively. Sho...

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  10. The (p+q)th term and (p-q)th terms of a G.P. are a and b respectively....

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  11. If the pth, th, rth terms of a G.P. are x, y, z respectively, prove th...

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  12. In a set of four numbers, the first three are in G.P. and the last thr...

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  13. If a^((1)/(x))= b^((1)/(y))= c^((1)/(z)) and a,b,c are in G.P., prove ...

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  14. If one G.M., G and two A.M's p and q be inserted between two given num...

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  15. Construct a quadratic equation in x such that the A.M. of its roots is...

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  16. The fourth term of a G.P. is greater than the first term, which is pos...

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  17. The first, eighth and twenty-second terms of an A.P. are three consecu...

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