Question

IF 3rd and 7th term of an A.P
is
18 and 30 then find the sum
of first 17 terms of and A.P.
b) 612
c) 624
d) 636​

Answer 1

Step-by-step explanation:

Answer is (b) 612

Given T3 = a + 2d

⇒ a + 2 d = 18 …(i)

and T7 = a + 6d

a + 6d = 30 …(ii)

From equation (i) and (ii),

4d = 12 ⇒ d = 3

Putting d = 3 in equation (i),

a + 2 × 3 = 18

⇒ a + 6 = 18

⇒ a = 12

17/2 ( 2 × 12 + ( 17 - 1 ) × 3 )

==> 17/2 × 72

=> 612

HOPE IT WILL HELPS U

PLEASE MARK ME AS BRAINLIST⭐⭐