Which number in the series is incorrect? 15, 16, 20, 30, 45, 70
- 16
- 20
- 30
- 70
Explanation
In this series, each number is formed by adding the square of a natural number (1^2, 2^2, 3^2, .....) to the preceding number.
- 15 + 1² = 16
- 16 + 2² = 20
- 20 + 3² = 29 ← should be 29, but given 30
- 29 + 4² = 45
- 45 + 5² = 70
So the correct sequence should be:
15, 16, 20, 29, 45, 70
Therefore, 30 is the incorrect number
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Last updated by NS on 01 MAY 2026
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