Question

Choose the correct choice in the following and justify:

30th term of the AP: 10, 7, 4, ..., is ______.

Options

• 97

•  77

• –77

• – 87

Answer 1

30th term of the AP: 10, 7, 4, ..., is –77.

Explanation:

Given that

A.P. 10, 7, 4, …

First term, a = 10

Common difference, d = a₂ − a₁ 

= 7 − 10

= −3

We know that, a_n = a + (n − 1) d

a₃₀ = 10 + (30 − 1) (−3)

a₃₀ = 10 + (29) (−3)

a₃₀ = 10 − 87

a₃₀ = −77

Hence, the correct answer is –77.