Question

If the sum of 1st 11 terms of an a.P is equal to sum of 1st 19 terms of that a.P then, find the sum of 1st 30 terms

Answer 1

Answer:

0

Step-by-step explanation:

sum of 11 terms = (11/2)(a + a+10d)

= 11a + 55d

sum of 19terms = (19/2)*(a+a+18d)

=19a + 171d

11a + 55d = 19a + 171d

-8a = 116d

2a +29d = 0

som of 30 terms = (30/2)(a + a +29d)

= 15* (2a + 29d)

= 15 * 0

= 0