1, 4, 9, 16, 20 - which is the odd one out?
Show answer & explanation
Correct answer: C
Explanation
All the numbers except 20 are perfect squares of consecutive natural numbers:
• 1 = 12
• 4 = 22
• 9 = 32
• 16 = 42
• 20 is not a perfect square (the next square is 52 = 25).
Therefore, 20 is the odd one out.