Question

If 7 times the $7^{th}$ term of an AP is equal to 11 times its ${11}^{th}$ term, then its ${18}^{th}$ term will be

• A. 7
• B. 11
• C. 18

Answer 1

$n^{th}termofAP=a+(n-1)d7times{7}^{th}termofanAP=11timesits{11}^{th}term7(a+6d)=11(a+10d)\Rightarrow 4a+68d=0\Rightarrow a+17d=018thterm=a+17d=0$