Question

The 5th term of
an A.P is 50. Find
the sum of first 9 terms
​

Answer 1

Answer:

nth term t

n

=a+(n−1)d

a= First term

d= Common difference

n= number of terms

t

n

=n

th

term

Given

T

5

+T

9

=30

a+4d+a+8d=30

2a+12d=30

a+6d=15

a=−6d+15

now

T

25

=3T

8

a+24d=3(a+7d)

24d−21d=3a−a

3d=2a

3d=2(6d−15)

15d=30

d=2

a=15−6×2

a=3

The AP is 3,5,7,9.........