Question

The third term of an A.P is 1/5 an the fifth term is 1/3. Show that the sum to 15 terms of the A.P is 8.

Answer 1

a+2d=1/5 --(1)
a+4d=1/3 --(2)
--(2) subtract --(1)
d=1/15
In --(1)
a=1/5 - 2/15
a=1/15
S=n/2 ×(2a+(n-1)×d)
S=15/2 ×(2×1/15+14×1/15)=8