Question

The sum of the first 10 terms of an A.P. is 200 and the sum of the
15 terms is 375. Find the sum of the first 20 terms.

please answer fast​

Answer 1

10/2 * (2a + (10-1)d) = 200

5(2a + 9d) = 200

2a + 9d = 40 .........(i)

15/2 * (2a + (15-1)d) = 375

2a + 14d = 50 ..........(ii)

(ii) - (i)

5d = 10

d=2

putting d=2 in (i)

2a + 18 = 40

a = 11

sum of 20 terms = 20/2 * (2*11 + 19*2)

= 10 * (22+38) = 600

Answer 2

Answer:

Hope it helps you a lot!!!!!!!