# 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

**Solution:**

We know that,

Probability = Number of possible outcomes / Total number of outcomes

As it is given in the question that the probability of drawing a blue ball is double that of a red ball, that means

2 × probability of drawing red ball = probability of drawing the blue ball.

Now, Number of red balls = 5

Let the number of blue balls be x

Total number of balls = x + 5

Probability of drawing red ball = Number of possible outcomes / Total number of outcomes

= 5/(x + 5)

Probability of drawing blue ball = Number of possible outcomes / Total number of outcomes

= x/(x + 5)

Since the probability of drawing a blue ball is double that of a red ball

x/(x + 5) = 2 [5/(x + 5)]

x = 10

Hence the number of blue balls = 10

Check out more about the terms of probability.

**ā Check: **NCERT Solutions for Class 10 Maths Chapter 15

**Video Solution:**

## 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

NCERT Solutions for Class 10 Maths Chapter 15 Exercise 15.2 Question 3

**Summary:**

If a bag contains 5 red balls and some blue balls, and the probability of drawing a blue ball is double that of a red ball, then the number of blue balls in the bag is 10.

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