Question

find the sum of the following AP 1+4+7+............73​

Answer 1

Answer:

a =1

d=4-1=3

last term=73

An =a+(n-1)d

63=1+(n-1)3

62=3n-3

65=3n

n=13

sum (Sn)=n/2(a+l)

13/2(1+73)

= 13/2(74)

13(37)

=481

481 is the answer