Question 697490: there are 7 yellow, 6 blue, 9 red, and 3 green ribbons in a drawer. once a ribbon is selected, it is not replaced. find each probability P(two ribbons that are not blue)
Answer by Positive_EV(69)   (Show Source):
You can put this solution on YOUR website! The probability of getting two ribbons that are not blue is equal to the probability the first ribbon is not blue times the probability the second ribbon is not blue. There are 7+6+9+3 total ribbons in the drawer, of which 6 are blue. That means there are 19 ribbons in the drawer that are not blue.
The probability of drawing a not blue ribbon is equal to the number of not blue ribbons divided by the total number of ribbons, so the probability of not drawing a blue ribbon on the first draw is 19/25.
After this draw, the ribbon is not replaced. There are now only 24 ribbons in the drawer now, of which 18 are not blue. The probability of the second ribbon drawn not being blue is thus 18/24.
The probability that both ribbons are not blue is the product, or (19/25)*(18/24) = 57/100 = .57.
|
|
|
