Question

find the sum of the first 12 term of the following AP 11 16, 21, 26

Answer 1

AP= 11,16,21,26,31,36,41,46,51,56,61,66
a=11, n=12, d=5,S=?
S=n/2(2a+(n-1)d)
S=6(2(11)+(12-1)5)
S=6(22+55)
S=6(77)
S=462