Multiple choice

In each of the following series only one number is wrong. You have to find out that wrong number. $20 10 11 15 30 75$

  1. 20

  2. 11

  3. 15

  4. 75

  5. None of these

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pattern analysis: 20÷2=10, 10+1=11 should be 10+2=12, 12÷2=6 but we have 15, 15×2=30, 30+15=45 should be 30×2.5=75. The pattern is ÷2, +2, ÷2, +2... But 11 breaks it (should be 12). Also 15 breaks alternate pattern. Option B (11) is the clearest wrong number.