Multiples of 100 are easy to spot because they all end in at least two zeros.
The number 100 ends in two zeros and so do all its multiples.
Examples
200, 400, 900, 1200, 2000, 300000 are multiples of 100.
They all end in at least two zeros.
50, 240, 1430, 1650 are NOT multiples of 100.
None of them ends in two zeros.