Question

Find the sum of first $22$ terms of an A.P in which the common difference $7$ and 22nd term is $149$.

Answer 1

common difference $\left(d\right)$=7

$T_{22}=a+(22-1)7$

$149=a+21\times 7$

$a=149-147=2$

so $s_n=\frac{n}{2}[a+l]$

$=\frac{22}{2}[2+149]$

$=11\times 151=1661$