Question

In an AP
given l=28,s=144, and there are total 9terms find a

Answer 1

SN = n/2 (a+l)

144= 9/2(a+28)

288= 9a + 252

36= 9a
a= 4

Answer 2

Answer:

S=144 l=28 n=9

Sn=n/2(a+l)

9/2(a+28)=144

a+28=32

a=4