A bag contains 5 red balls and some blue balls. If the probability of drawing a blue ball from the bag is thrice that of a red ball, the number of blue balls in the bag is:
10
15
20
25
Probability
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Question

A bag contains 5 red balls and some blue balls. If the probability of drawing a blue ball from the bag is thrice that of a red ball, the number of blue balls in the bag is: 1. 10 2. 15 3. 20 4. 25

KnowledgeBoat · Accepted Answer

Let the number of blue balls in the bag be x.

Total number of balls in bag = x + 5

The probability of drawing a red ball and a blue ball are:

$P$

The probability of drawing a blue ball is thrice (3 times) that of a red ball: P_b = 3 × P_r

Substituting values we get:

$\Rightarrow \dfrac{x}{x + 5} = 3 \times \dfrac{5}{x + 5} \\[1em] \Rightarrow x = 15.$

The number of blue balls in the bag is 15.

Hence, option 2 is the correct option.

Mathematics

A bag contains 5 red balls and some blue balls. If the probability of drawing a blue ball from the bag is thrice that of a red ball, the number of blue balls in the bag is:
10
15
20
25

Probability

Answer

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