Question

The ratio of the sum of 2 AP's is (7n+1):(4n+2), find the ratio of their 10th term?​

Answer 1

     

$S1_n:S2_n=(7n+1):(4n+2)$

We know that,

$S_n=n \times [\frac{n+1}{2}]^{th}\ term \\ \\ \\ S_n=n \times T_{[\frac{n+1}{2}]}$

Okay. Take n = 19. (You'll get why I took n = 19. If won't, plz ask me.)

$S1_{19}:S2_{19}=(7 \times 19 + 1):(4 \times 19 + 2) \\ \\ 19 \times T1_{[\frac{19+1}{2}]}:19 \times T2_{[\frac{19+1}{2}]}=(133+1):(76+2) \\ \\ T1_{[\frac{20}{2}]}:T2_{[\frac{20}{2}]}=134:78 \\ \\ T1_{10}:T2_{10}=\bold{67:39}$

∴ The ratio of 10th terms is 67:39.

Please, don't forget to ask me if you have any doubt in my answer.

Mark this answer as the brainliest. This is the simplest method for such questions.

Thank you. Have a nice day. :-))