Question

The first term of an AP is -76 and the sum of first 45 terms is -9360. Which of the following is the last term of this AP​

Answer 1

- 340

Explanation:

The sum to n terms of an AP is

`S_(n)` =
`(n)/(2)` ( a + l ) → a is the first term and l the last term

Here a = - 76 and
`S_(45)` = - 9360 , thus

`(45)/(2)` ( - 76 + l ) = - 9360

22.5(- 76 + l) = - 9360 ( divide both sides by 22.5 )

- 76 + l = - 416 ( add 76 to both sides )

l = - 340 ← the last term in the sequence