There are two formulae to find the sum of the terms of an AP.
In this case we know the following:
a=2,d=4,n=11
Sn=n2[2a+(n−1)d]
S11=112[2(2)+(10)4]
S11=5.5[4+40]
S11=242.
Find the sum of the first (i) 11 terms of the A.P.: 2,6,10,14,... (ii) 13 terms of the A.P.: -6,0,6,12,... (iii) 51 terms of the A.P.: whose second term is 2 and fourth term is 8.