Question

What is the common difference of the sequence 3, 12, 21, 30, 39?

A. 4
B. 11
C. 10
D. 9

Answer 1

(d)-9

Explanation:

12 – 3 = 9, 30 – 21 = 9, etc.

Answer 2

Explanation:

3 + 9 = 12,

12 + 9 = 21,

21 + 9 = 30,

30 + 9 = 36.

The common difference is 9. (D)