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a bag contains 5 red balls and some blue balls. if the probability of drawing a blue ball is thrice that of red ball, find the number of blue balls in the bag?
Let number of blue balls be x.

Total balls in bag are (5 + x) and as one balls is drawn so possible outcomes are (5 + x).

There are 5 red balls, so favourable outcomes for red balls are 5.

Probability of drawing a red ball = 5 / 5 + x .........(i)

There are x blue balls, so favourable outcomes for blue balls are x.

Probability of drawing a blue ball = x / 5 + x. ...........(ii)

According to given condition: x / 5 + x = 3. 5/ 5 + x ....from (i) and (ii)

x = 15.

Therefore, blue ball are 15.


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