math (probability)
2009-10-09 7:17 am
A bag contains 5 red balls, some green balls and blue balls. The no. of green and blue balls are in a ratio of 2:3. A ball is drawn at random from the bag. Given that the Probability of drawing a green vall is 3/10, find the no of green balls in the bag.
回答 (1)
2009-10-09 7:30 am
✔ 最佳答案
Let there are x green balls :
then there are 3x/2 blue balls .
So the bag total have 5 + x + 3x/2 balls
x / (5 + x + 3x/2) = 3/10
x = (5 + 5x/2)(3/10)
x = 3/2 + 3x/4
x/4 = 3/2
x = 6
the no of green balls in the bag = 6
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