Question

The following sequence is an arithmetic sequence what comes next ? 7,___,17

Answer 1

Since this is an arithmetic sequence, you can conclude that the addition to the number is constant.

Let x = the number asked

       k = constant number added to the sequence

7 + k = x

x + k = 17

Solve the system of equation:

7 + k + k = 17

7 + 2k = 17

2k = 10

k = 5

Therefore, the missing number is 12 (7 + 5).