which number comes next in this series 19,24,21,23,28,24

Question

which number comes next in this series and why? 19,24,21,23,28,25

Answer 1

21.............................

Answer 2

Series is 19, 24, 21, 23, 28, 24 (from the question title).

First differences:

+5, -3, +2, +5, -4. Since +5-3=+2, perhaps the next three differences would be +5-4=+1 making the next number 24+1=25.

Or, if the series was supposed to be 19, 24, 21, 23, 28, 25 (from the question details) with first differences:

+5, -3, +2, +5, -3, the next difference would also be +2, to match the first pattern, so the next number would be 25+2=27.