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Question
A bag contains 5 red balls and n green balls. If the probability of drawing a green ball is three times that of a red ball, then the value of n is ______.
Options
18
15
10
20
Solution
A bag contains 5 red balls and n green balls. If the probability of drawing a green ball is three times that of a red ball, then the value of n is 15.
Explanation:
Given, Number of red ball = 5
Number of green ball = n
∴ Total ball = n + 5
Now P(red ball) = `5/(n + 5)`
and P(green ball) = `n/(n + 5)`
Now, according to the question
`n/(n + 5) = (3 xx 5)/(n + 5)`
n = 15
So, number of green ball = 15
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