Three of the following four numbers are alike in a certain way and one is different. Choose the number that does not belong to the group.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 301
Check whether each number is a prime number (divisible only by 1 and itself). A number below 300 is prime if no prime up to 17 divides it, because \( 17 \times 17 = 289 \).
Option (1) 301 — \( 301 = 7 \times 43 \), so 301 is not a prime.
Option (2) 293 — 293 is not divisible by 2, 3, 5, 7, 11, 13 or 17: a prime.
Option (3) 239 — 239 is not divisible by 2, 3, 5, 7, 11 or 13 (\( 16 \times 16 = 256 \) is already more than 239): a prime.
Option (4) 257 — 257 is not divisible by 2, 3, 5, 7, 11 or 13 (\( 17 \times 17 = 289 \) is more than 257): a prime.
293, 239 and 257 are prime numbers; 301 is not, so 301 is the odd one out.