The first term of an arithmetic progression is and the last term is

MATHEMATICS · Single correct · CBSE · Mathematics · Arithmetic Progressions · Arithmetic Progressions

Problem

The first term of an arithmetic progression is

12

and the last term is

57

. If the sum of all its terms is

345

, how many terms does the progression contain? (a)

11

(b)

15

(c)

10

(d)

9