Question

If the seventh term of an AP is 25 and the common difference is 4, then find the 15th term of AP.

• A. 55
• B. 50
• C. 57
• D. 52

Answer 1

The correct option is C 57

Let $a$ be the first term and $d$ be their common difference of the AP.
Then, $nth$ term of the AP $T_n=a+(n-1)d$
Given, $T_7=25$
$=>a+(7-1)d=25$
$=>a+6d=25$
$=>a+6\times 4=25$
$=>a=1$
So, $T_{15}=a+(15-1)d=1+14\left(4\right)=57$