To find the next number in this series, we need to observe the pattern or rule that governs the sequence. Let's look at the differences between consecutive terms:
100 - 25 = 75
225 - 100 = 125
400 - 225 = 175
From the differences, we can see that they are increasing by 50 each time. Therefore, we can predict that the next difference will be 175 + 50 = 225.
To find the next term, we add this difference to the previous term:
400 + 225 = 625
Therefore, the next number in the series is 625.
Among the given options, the correct answer is C) 625.