SOLUTION: A bag contains 8 red balls and some white balls, all of the same size. If the probability of drawing at random a white ball from the bag is half the probability of drawing a red ba
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Question 1210325: A bag contains 8 red balls and some white balls, all of the same size. If the probability of drawing at random a white ball from the bag is half the probability of drawing a red ball, find the number of white balls in the bag Answer by Edwin McCravy(20060) (Show Source):
You could just think out that there would have to be only half as many
white balls as red balls, and half of 8 is 4.
Otherwise,
...A bag contains 8 red balls and some white balls, all of the same size....
There are 8 red balls and N white balls
There are N+8 balls in the bag.
The probability of drawing a red ball is 8 out od N+8 or
The probability of drawing a white ball is N out of N+8 or
...If the probability of drawing at random a white ball from the bag is half
the probability of drawing a red ball,...
Go to https://www.wolframalpha.com/
Type in N/(N+8) = (1/2)(8/(N+8))
Press ENTER
See N = 4, so there are 4 white balls in the bag.
Edwin
