Question

If an ap given a=5,d=3,an=50.Find the value of n and sn

Answer 1

an=a+(n-1)d

50=5+(n-1)3

50=5+3n-3

50=2+3n

50-2=3n

48=3n

n=48/3

n=16

sn=n/2(a+an)

=16/2(5+50)

=8(55)

therefore sn=440

hope it helped u.....