In the statistics, 1 in __ children have autism. Which number completes the statement?

In the statistics, 1 in __ children have autism. Which number completes the statement?

• A. 10
• B. 31
• C. 42
• D. 5

Answer: (B)

Understanding how to read “1 in N” helps you see what the sentence is describing. Saying “one in N children” means the probability is 1 divided by N, or about 1/N of the children. If you use 31, you get 1/31 ≈ 0.032, which is about 3.2%. Put another way, in a group of 31 children, you would expect roughly one child to have autism. The remaining options would imply noticeably different prevalences: 1 in 10 is 10%, 1 in 42 is about 2.4%, and 1 in 5 is 20%. The number that matches the common framing in this context is 31, giving a small but plausible prevalence.

Understanding how to read “1 in N” helps you see what the sentence is describing. Saying “one in N children” means the probability is 1 divided by N, or about 1/N of the children.

If you use 31, you get 1/31 ≈ 0.032, which is about 3.2%. Put another way, in a group of 31 children, you would expect roughly one child to have autism. The remaining options would imply noticeably different prevalences: 1 in 10 is 10%, 1 in 42 is about 2.4%, and 1 in 5 is 20%. The number that matches the common framing in this context is 31, giving a small but plausible prevalence.