Multiple choice

Find the wrong number in the following series. 1 2 3 5 15 30 105

  1. 2

  2. 3

  3. 5

  4. 15
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Series: 1, 2, 3, 5, 15, 30, 105. Pattern: 1*1=1, 1*2=2, 2*1.5=3, 3*2=6 (not 5), 6*2.5=15, 15*2=30, 30*3.5=105. The pattern is multiplying by 1, 1.5, 2, 2.5, 3, 3.5. The term 5 is wrong; it should be 6.

AI explanation

The correct pattern for this series multiplies consecutive natural numbers in stages, where 1 * 2 = 2, 2 * 3 = 6, 6 * 4 = 24, 24 * 5 = 120 and so on. In the given sequence, the number 5 is incorrect because the fourth term should be 6. Therefore, 5 is the wrong number in the series.

Keep practicing — related questions