Multiple choice

Directions: In the following number series one number is wrong. Find out the wrong number. 99, 98, 95, 90, 82, 74, 63

  1. 98

  2. 82

  3. 95

  4. 63

  5. 74
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Differences: 99-98=1, 98-95=3, 95-90=5, 90-82=8 (should be 7), 82-74=8, 74-63=11. The sequence of differences should be odd numbers: 1, 3, 5, 7, 9, 11. 90-7=83, 83-9=74. Thus, 82 is the wrong number.

AI explanation

The differences between the consecutive terms of the series are calculated using the subtracting prime numbers method. The differences are 1, 3, 5, 8, 8 and 11, which shows a deviation at the last few steps. The intended pattern of differences is consecutive prime numbers starting from 1: 1, 3, 5, 7, 11 and 13, meaning the fifth difference should be 7 instead of 8. Applying this, 90 minus 7 gives 83, which means 82 is the wrong number.

Keep practicing — related questions