Question

In an A.P., a = –3 and S₁₇ = 357. The value of a₁₇ is ______.

Options

• 47

• 39

• 45

• 42

Answer 1

In an A.P., a = –3 and S₁₇ = 357. The value of a₁₇ is 45.

Explanation:

Given: a = –3

S₁₇ = 357

n = 17

Using the formula for sum of n terms:

`S_n = n/2 (a + a_n)`

`357 = 17/2 (-3 + a_17)`

`357 xx 2/17 = -3 + a_17`

21 × 2 = –3 + a₁₇

42 = –3 + a₁₇

a₁₇ = 42 + 3

a₁₇ = 45