Fourth term of an arithmetic progression is 8. What is the sum of the first 7 terms

• Progressions

Fourth term of an arithmetic progression is 8. What is the sum of the first 7 terms of the arithmetic progression?

1. 7
2. 35
3. 56
4. 64

Answer

n^th term of Arithmetic Progression = a + (n-1)d

4^th term = a + 3d = 8

Sum of first 7 terms = 7/2 (2a + 6d)

2a + 6d = 8 * 2

= 7/2 * 8 * 2 = 56

The correct option is C.