Question

A bag contains 5 red balls and some blue balls. If the probability of drawing a blue ball
is double that of a red ball, determine the number of blue balls in the bag.
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Answer 1

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It is given that the total number of red balls =5

Let the total number of blue balls = x

So, the total no. of balls = x + 5

P(E) = (Number of favourable outcomes/ Total number of outcomes)

∴ P (drawing a blue ball) = [x/(x + 5)] ——–(i)

Similarly,

P (drawing a red ball) = [5/(x + 5)] ——–(i)

From equation (i) and (ii)

x = 10

So, the total number of blue balls = 10

Answer 2

Answer:

Let the number of blue balls be x.

Number of red balls = 5

Total number of balls = x + 5

P (getting a red ball)

P (getting a blue ball)

Given that

But number of balls cannot be negative.

Hence, the number of blue balls is 10.