Question

How many numbers between 1 and 100 (inclusive) are divisible by 4 or 5

Answer 1

Answer: 40 numbers

Step-by-step explanation:

For us to do this, we will have to group the numbers in groups of 20.

You should note that from 1 to 20, there are 5 numbers that are divisible by 4 which are 4, 8, 12, 16, 20.

Also, there are 5 "20s" that are in 100, therefore 5 X 5 = 25 numbers that are divisible by 4.

Likewise, there are also 4 numbers that are divisible by 5 which are 5 , 10 , 15 , 20.

There are also 5 "20s" in 100, thos will give 5 x 4 = 20 numbers that are divsible by 5.

However, we have to subtract the numbers that are divisible by both 4 and 5 in order to prevent double counting.

These are 20, 40, 60, 80 and 100.

Thereforee, we will have:

25 + 20 - 5 = 40 numbers that are divisible by 4 or 5 from 1-100.