A bag contains 6 red balls and some blue balls.

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A bag contains 6 red balls and some blue balls. If the probability of drawing a blue ball is twice that of a red ball, find the number of balls in the bag.

Solution:

In a bag, there are 6 red balls, and some blue balls
Probability of blue ball = 2 × probability of red ball
Let number of blue balls = x
and number of red balls = 6
Total balls = x + 6
Probability of a blue ball = 2
⇒ \frac { x }{ x+6 } =2\times \frac { 6 }{ x+6 }
⇒ \frac { x }{ x+6 } =\frac { 12 }{ x+6 }
⇒ x = 12
Number of balls = x + 6 = 12 + 6 = 18

A bag contains 24 balls of which x are red, 2x are white and 3x are blue. A blue is selected at random. Find the probability that it is
(i) white
(ii) not red.

Solution:

In a bag, there are 24 balls
Since, there are x balls red, 2 × balls white and 3 × balls blue
x + 2x + 3x = 24

ML Aggarwal Class 10 Solutions for ICSE Maths Chapter 22 Probability Ex 22 Q34.1

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