Answer: What Comes Next? #372

The answer is B: 30.

The rule

Add 1, then add 8, then 1, then 8, 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 = [1, 8]
number = 3
for step in range(7):
    print(number)
    number = number + adds[step % 2]

When you run it, Python prints:

3
4
12
13
21
22
30