Question

Jill writes some numbers on pieces of papers, folds them, and drops them in a jar. Then, Jack takes out five pieces of papers.
The numbers on them are 1, 3, 6 10, and 15.

Looking at the numbers, Jill says that they are in a series.

Find the next one in the series.

• A. 21
• B. 25
• C. 22
• D. 20

Answer 1

The correct option is A 21

1 + 2 = 3
3 + 3 = 6
6 + 4 = 10
10 + 5 = 15

Thus, there is an addition of the consecutive number to each number in the series.
This means that the next number can be obtained by adding 6 to 15.

We get:
Thus, the next number in the series will be 21.