Answer: What Comes Next? #342

The answer is B: 31.

The rule

Add 3, then add 7, then 3, then 7, and so on. The pattern of adding takes turns.

The pattern as Python code

Here is a tiny Python program that follows the same rule. Type it into IDLE and run it to print the whole pattern, including the answer.

adds = [3, 7]
number = 1
for step in range(7):
    print(number)
    number = number + adds[step % 2]

When you run it, Python prints:

1
4
11
14
21
24
31