Multiple choice

Fill in the missing number in the series: 7, 13, 21, ____, 43, 57

  1. 35

  2. 30

  3. 31

  4. 34
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The differences are: 13-7=6, 21-13=8, 43-x, 57-43=14. The differences are increasing by 2: 6, 8, 10, 12, 14. So 21 + 10 = 31.

AI explanation

The differences between the consecutive terms of this arithmetic progression are calculated. The sequence increases by 6, 8, 10, 12, and 14 respectively. Adding 10 to 21 gives the missing term of 31.

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