Multiple choice

Directions: In the following number series, one term is incorrect. Find the incorrect term. 5, 7, 11, 20, 35, 67

  1. 67

  2. 35

  3. 20

  4. 11
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Differences: 7-5=2, 11-7=4, 20-11=9, 35-20=15, 67-35=32. The differences should be powers of 2 (2, 4, 8, 16, 32). 20 is incorrect because 11+8=19, and 19+16=35.

AI explanation

The pattern governing this series is that each term is found by multiplying the previous term by 2 and then subtracting an increasing odd number starting from 1. Checking the steps, (5 * 2) - 1 = 9, which makes 7 incorrect based on a strict pattern, but let us look at the additive differences: +2, +4, +9, +15, +32. If the intended rule is x * 2 - 3, the sequence would be 5, 7, 11, 19, 35, 67, which makes 20 the incorrect term. Thus, 20 disrupts the established logic.

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