Multiple choice

complete the sequence   1...  4...  7...  11...  15...  __...

  1. 18

  2. 21

  3. 19

  4. 20

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

The differences between consecutive terms are +3, +3, +4, +4. Following this pattern, the next difference should be +5. Adding 5 to 15 gives 20.