Question

If and A. P given a=5, d=3,an=50 find n and Sn

Answer 1

an=a+(n-1)d
50=5+(n-1)3
45/3=n-1
15=n-1
n=16



Sn=n/2(a +an)
Sn=16/2(5+50)
Sn=8(55)
Sn=440