Find the sum of first 22 terms of an AP in which d=7 and 22nd term is 149.

Given d=7, a22=149
We want to find S22.
an=a+(n-1)d ⇒ a22=a+(22-1)7 ⇒ 149=a+(21)(7) ⇒ 149=a+147 ∴a=2
We have Sn=n/2(a+an) then S22=22/2(2+149)=11×151=1661