Problem:
A bag contains only blue balls and green balls. There are blue balls. If the probability of drawing a blue ball at random from this bag is , then the number of green balls in the bag is
Answer Choices:
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Solution:
Since one quarter of the balls are blue and there are blue balls, there must be balls in the bag. Thus there are green balls.
Since one quarter of the balls are blue, three quarters of them must be green. Thus there are three times as many green balls as blue balls, so there are green balls.
Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions