Question

If your are picking a number between 1-20 what is the probability that you will pick an even number number or a multiply of three?

Answer 1

65%

There are only 7 numbers that don't fit this criteria. Therefore, there are 13 that do. 13/20 = .65*100 = 65%

Answer 2

Even numbers always end with a digit of 0, 2, 4, 6 or 8. The set of even numbers between 1 and 20 are 2,4,6,8,10,12,14,16,18.The  numbers which are multiples of 3 and lie between 1 and 20 are 3,6,9,12,15,18.

Total numbers which are even and multiple of 3 between 1 and 20 are 2,3,4,6,8,9,10,12,14,15,16,18. There are 13 numbers in all.

There are 20 numbers between 1 and 20.

Probability of picking  an even number number or a multiply of three = $\frac{13}{20}$