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**