What is the mean of the first 12 prime numbers (correct to two decimal places)?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 16.42
List the primes in order starting from 2 (1 is not a prime), add them and divide by how many there are.
First 12 primes: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37
Sum \(=197\)
Mean \(=197\div12=16.4167\ldots\)
The mean is 16.42.
Why the other options are incorrect
Option (1) 19.67 — Incorrect. This leaves out 2, the only even prime, and takes the next 12 primes instead.
Option (2) 13.42 — Incorrect. This counts 1 as a prime; 1 is not a prime, so the first 12 primes run from 2 to 37.
Option (4) 17.91 — Incorrect. This divides the sum 197 by 11 instead of by 12.