What is the mean of the first 10 prime numbers (correct to two decimal places)?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 12.90
List the primes in order starting from 2 (1 is not a prime), add them and divide by how many there are.
First 10 primes: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29
Sum \(=129\)
Mean \(=129\div10=12.9\)
The mean is 12.90.
Why the other options are incorrect
Option (1) 15.80 — Incorrect. This leaves out 2, the only even prime, and takes the next 10 primes instead.
Option (3) 10.10 — Incorrect. This counts 1 as a prime; 1 is not a prime, so the first 10 primes run from 2 to 29.
Option (4) 14.33 — Incorrect. This divides the sum 129 by 9 instead of by 10.