Question

Find a 3-digit number that is divisible by 2 and 5​

Answer 1

Answer:

The positive integers less than 11 are 1,2,3,4,5,6,7,8,9,10 Half of them are divisible by 2 2,4,6,8,10 One fifth of them are divisible by 5 5,10 These lists both include 10 which is divisible by 2 and 5. When counting the number of integers in the two lists combined we can only count the 10 once.