Question

What is the sum of the first 9 terms of an arithmetic progression if the first term is 7 and its least term is 55 ?
1. 279
2. 289
3. 212
4. 219

Answer 1

Correct Answer - Option 1 : 279

Given:  In an arithmetic progression the first term is 7 and its least term is 55

Concept used: In an AP S_n = n/2 ( 1st term + last term )

Calculation: Where n = 9, first term = 7 and last term is 55

⇒ 9/2 (7 + 55)

⇒ 9/2 (62)

∴ 279