Asked by FEBIN

the sum of the n termsof an ap whose first term is 5 and common difference is 36 is equal to the sum of 2n terms of another AP whose first term is 36 ans common difference is 5. Find n?

Answers

Answered by Reiny
sum of n terms of 1st = (n/2)(10 + 36(n-1))
= (n/2)(36n - 26)
sum of 2n terms of 2nd = (2n/2)(72 + 5(2n-1))
= n(10n + 67)

(n/2)(36n - 26) = n(10n + 67)
divide by n, and multiply by 2
36n - 26 = 20n + 134
16n = 160
n = 10

check:
sum(10 for 1st) = 5(10 + 36(9)) = 1670
sum(20 for 2nd) = 10(72 + 19(5)) = 1670
all is good!
Answered by ravi
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Answered by ravi
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Answered by Prince Sharma
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Answered by deepthi
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Answered by Sahil
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Answered by siddharth
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Answered by Anonymous
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Answered by MANYA
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