# A bag contains, white, black and red balls only. A ball is drawn at random from the bag.If the probability of getting a white ball is 3/10 and that of a black ball is 2/5 then find the probability of getting a red ball. If the bag contains 20 black balls, then find the total number of balls in the bag. - Mathematics

A bag contains, white, black and red balls only. A ball is drawn at random from the bag.If the probability of getting a white ball is 3/10 and that of a black ball is 2/5 then find the
probability of getting a red ball. If the bag contains 20 black balls, then find the total number of balls in the bag.

#### Solution

n(total balls in the bag) = x

"P(getting a black ball)" =2/5=20/50="number of black balls"/"total number of balls"

Number of black balls in the bag =20

Total number of balls = 50

"P(getting a white ball)" =3/10=15/50="number of white balls"/"total number of balls"

Number of white balls in the bag = 15
Number of red ball

= Total number of ball – (Number of black ball + Number of white ball)
= 50 – (20 + 15)
= 50 – 35
= 15
Total number of balls in the bag = 15.

Concept: Basic Ideas of Probability
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2014-2015 (March) All India Set 3

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