Question

.The sum of n term of two AP are in the ratio (2 n+1) : (2 n-1). the ratio of the 10th terms is

Answer 1

We know that,

Any n th term of an AP

= sum of n terms-sum of (n-1) ters

Given here,

Sum of n terms are in ratio 2n+1:2n-1

So,

The ratio of 10th terms are,

{(2(10)+1):(2(10)-1)}-{(2(9)+1):(2(9)-1)}

{21:19}-{19:17}

21/19–19/17

(357–361)/323

-4/323

Negative signs here indicate that on of the term form both the APs is negative .

Therefore the ratio is 4/323 (Ans.)