A bag contains balls with the numbers 1 through 100 . If you draw a ball at random, what is the probability that you get a number which is not a multiple of 7 ?

Answer 1

It is necessary to first determine how many balls in the bag ARE multiples of 7

7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, and 98 are all multiples of 7.

There are 14 numbers in this set. There are 100 - 14 = 86 numbers that are NOT multiples of 7.

Thus the probability of drawing a ball from the bag that is not a multiple of 7 is 86/100 = 0.86