Question: how many numbers between 1 and 100 are divisible by 4 and 9?
Answer: There are 11 numbers divisible by 9 between 1 and 100, and 25 numbers divisible by 4 between 1 and 100. So there are 11 + 25 = 36, so 36 numbers divisible by one or the other, but this also includes every number which is divisible by both 9 and 4 twice.