Question

The numbers 1-40 are written on pieces of paper and put in a box. Two pieces of paper are randomly selected. What is the probability both numbers will be multiples of 4?

Answer 1

So we have 40 possible numbers to choose from in the beginning. There are 10 numbers which are multiples of 4, so the probability of drawing one multiple of 4 is 10/40 = 1/4.

Since we drew a number previously, we now have 39 possible numbers to choose from. Since we have to draw two numbers that are multiples of 4, we can assume that we've already drawn one, meaning that we have 9 numbers left. Therefore, the probability of drawing a second number that's a multiple of 4 is 9/39.

Now, since we need to have drawn two numbers that are multiples of 4, we multiply the first probability by the second: 1/4 * 9/39 = 9/156 = 3/52.