Question

Difficulty: EasyNumber and Alphabet Series

Consider the following numerical series: 4,7,12,19,28,4, 7, 12, 19, 28, \dots. What is the next number in this series?

Answer: 39

Answer

The next number in the series is 3939.
The difference between consecutive terms increases by 2 each time (+3,+5,+7,+9+3, +5, +7, +9). The next difference to add is +11+11, yielding 28+11=3928 + 11 = 39.

Step-by-Step Solution

1
Calculate the difference between each pair of consecutive terms.
The differences are 3,5,7,93, 5, 7, 9.
Identifying the first-order difference sequence reveals the pattern of progression.
2
Find the next value in the difference sequence.
The next odd number after 99 is 1111.
The pattern of differences consists of consecutive prime/odd increments (specifically, odd numbers +2+2 each step).
3
Add the calculated difference to the final given term of the series.
28+11=3928 + 11 = 39
Applying the pattern to find the subsequent term.

Key Concept

Number series completion using a sequence of increasing odd differences.
Rate this question