This question was previously asked in

SSB Head Constable 2018 Official Paper (Conducted on 3 Jan 2021)

- 3, 4
- 4, 7
- 5, 12
- 20, 21

Option 4 : 20, 21

Let's discuss the concepts related to Classification and Number Based. Explore more from Logical Reasoning here. Learn now!

By checking option:

(1) 3, 4 → 3 is a prime number and 4 is an even number.

(2) 4, 7 → 4 is an even number and 7 is a prime number.

(3) 5, 12 → 5 is a prime number and 12 is an even number.

**(4) 20, 21 → 20 is an even number but 21 is not a prime number.**

Implies every pair has an even number and a prime number except 20, 21.

Hence, **20, 21 **does not belong to the others.

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