Multiple choice

In the following series, find out the missing number. 20, 23, 30, 43, 64, ?

  1. 95

  2. 90

  3. 100

  4. 105

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Differences: 23-20=3, 30-23=7, 43-30=13, 64-43=21. Second differences: 7-3=4, 13-7=6, 21-13=8. Next second difference is 10. Next first difference is 21+10=31. Next number is 64+31=95.

AI explanation

The differences between consecutive terms are formed by adding consecutive prime numbers: 3, 7, 13 and 21. The next difference should be 31, so adding 31 to the last term of 64 gives 95.

Keep practicing — related questions