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![[Post New]](/templates/default/images/icon_minipost_new.gif) 16 Jul 2007 11:35:53 IST
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if the ratio between the sum of n terms of 2 AP's is 3n+8/7n+15 Then the ratio between their 12 th term is Ans 7:16 Please give me a detailed solution i shall rate you
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16 Jul 2007 12:35:04 IST
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Let the 1st terms be A and a, and common difference be D and d respectively.
Now, n/2(2A+(n-1)D)/n/2(2a+(n-1)d/) = the given ratio.
Cancelling,n, we get:
(A+(n-1)/2D)/(a+(n-1)/2d) = the ratio.
Put (n-1)/2 = 11 => n-1 = 22 => n=23.
The ratio is: 77/176 = 7/16.
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