Question

A box contains twenty cards numbered trough 20. One card is to be randomly drawn from the box.

What is the probability that the card drawn will show a multiple of 6, a multiple of 7,or a multiple of 8?

A=1/20

B=1/3

C=7/20

D=1/2

Answer 1

Cards that are multiples of 6 -> 6, 12, 18
Cards that are multiples of 7 -> 7, 14
Cards that are multiples of 8: -> 8, 16

P(multiple of 6) + P(multiple of 7) + P(multiple of 8) =
[P(6) +P(12) +P(18)] + [P(7) +P(14)] + [P(8) + P(16)]

Answer 2

And since each card has an equal chance of being drawn with probability 1/20, each probability P(.) = 1/20

Answer 3

Thank you very much! :)