Probabitity

Question

a bag contains pieces of paper numbered 1-30. One card is randomly selected. What is the probability that the number on the card is a multiple of 5 or a multiple of 3 

Answer 1

Multiples of 5:  5, 10, 15, 20, 25, 30

 

Multiples of 3:  3, 6, 9, 12, 15, 18, 21, 24, 27, 30

 

Of the 30 choices, 6 are multiples of 5, 10 are multiples of 3, and 2 are multiples of both 3 and 5.  

 

P(multiple of 5 or 3) = P(multiple of 5)+P(multiple of 3)-

                                                                                     P(multiple of both)

 

                                    = 6/30 + 10/30 - 2/30 = 14/30 = 7/15