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Odd Pair Out Questions with Solutions

This is Classification applied to pairs instead of single items — three pairs share a hidden numeric relationship, and one pair breaks it. Here’s the approach, four fully worked examples, and a few to try yourself.

The approach, quickly

  • Check the relationship within each pair individually first (does the second number look like a square, cube, a simple multiple, or a product of the first number with something?) before comparing across pairs.
  • Test your hypothesized relationship against every pair, not just the first two — a rule that fits three out of four pairs (and breaks only on the fourth) is the intended rule.
  • Common relationships to try, in order: second = first², second = first³, second = first × a fixed number, second = first × (first + a fixed number).
  • Once you’ve confirmed a relationship holds for three pairs, calculate what the fourth pair’s second number SHOULD be under that same relationship — this confirms the odd pair with certainty, rather than just a hunch.

Worked examples

1. Find the pair that does not belong with the others: (3,9), (4,16), (5,20), (6,36)

Solution

  1. Most pairs follow "second = first²": 3²=9, 4²=16, 6²=36 — all match.
  2. For (5,20): 5² = 25, not 20 — this pair breaks the pattern.

Answer: (5,20)

2. Find the pair that does not belong with the others: (8,4), (12,6), (20,10), (15,6)

Solution

  1. Most pairs follow "second = first ÷ 2": 8÷2=4, 12÷2=6, 20÷2=10 — all match.
  2. For (15,6): 15÷2=7.5, not 6 — this pair breaks the pattern.

Answer: (15,6)

3. Find the pair that does not belong with the others: (2,8), (3,27), (4,64), (5,100)

Solution

  1. Most pairs follow "second = first³": 2³=8, 3³=27, 4³=64 — all match.
  2. For (5,100): 5³=125, not 100 — this pair breaks the pattern.

Answer: (5,100)

4. Find the pair that does not belong with the others: (5,30), (6,42), (7,56), (8,56)

Solution

  1. Most pairs follow "second = first × (first+1)": 5×6=30, 6×7=42, 7×8=56 — all match.
  2. For (8,56): 8×9=72, not 56 — this pair breaks the pattern.

Answer: (8,56)

Try these yourself

Find the shared relationship from three of the four pairs, then check against the answer.

1. Find the pair that does not belong with the others: (7,49), (8,64), (9,72), (10,100)

Answer: (9,72)

2. Find the pair that does not belong with the others: (10,5), (16,8), (24,11), (20,10)

Answer: (24,11)

3. Find the pair that does not belong with the others: (2,8), (3,27), (4,64), (5,126)

Answer: (5,126)

Where this comes up

Odd Pair Out is a regular topic in the Reasoning/General Intelligence section of every exam Pariksha Saathi covers — SSC CGL, SSC MTS, SSC CHSL, IBPS PO, IBPS Clerk, SBI PO and SBI Clerk.

Practice more Odd Pair Out questions

This page covers the approach and a handful of worked examples. Pariksha Saathi has full topic-wise practice sets for Odd Pair Out (and every other Reasoning/Quant/English topic) with instant scoring and explanations — free, no account required.

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