GATE 2024 PH – Question 2
Find the odd one out in the set: {19, 37, 21, 17, 23, 29, 31, 11}
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Correct answer: (A) 21
Explanation
Look at what the numbers in the set have in common.
$$\{19,\ 37,\ 21,\ 17,\ 23,\ 29,\ 31,\ 11\}$$
- 19, 37, 17, 23, 29, 31 and 11 are all **prime numbers**.
- 21 is not prime: $21=3\times7$.
The odd one out is **21** (option A).