Question

The third term of an ap is 18 and the 7th term is 30 find the sum of 17 terms

Answer 1

Answer :

60

Step-by-step explanation:

3rd term of AP = a + 2d ---(1)

7th term of Ap = a + 6d ----(2)

subtract (1) - (2)

a + 2d - a - 6d = 12 - 30

-4d = -12

d = -12/-4

= 3

from equation 1

a = 18 - 2d

substitute the value d = 3

then , a = 18 - 2×3 = 18 - 6 = 12

therefore 17th term of AP is

a + 16d = 12 + 16×3 = 12 + 48 = 60