Question

is the sum of the first n term of arithmetic progression,13,17,21,... is 846, find the no. of term's and last term.

Answer 1

A.P: 13, 17, 21, ....... 846
a1= 13, an = 846, d=4

Well, the last term is given I.e 846

and we know that an=a+(n-1)d
so 846 = 13 + (n-1)4
(n-1)4 = 833
n-1= 833/4
n= 833/4+1

Hope it helped.
Regards.

Answer 2

no. of terms is 36 and the last term is 153 , I guess