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A bag contains white, black and red balls only. A ball is drawn at random from the bag. The probability of getting a white ball is $310$ and that of a black ball is $25$ . 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.

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\frac{3}{10}

50

\frac{2}{10},

60

\frac{3}{10},

30

\frac{1}{10},

40

answer is A.

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Detailed Solution

Given, a bag contains white, black and red balls only. A ball is drawn at random from the bag. The probability of getting a white ball is

310

and that of a black ball is

25

. The bag contains 20 black balls.
The probability of an event to be occurred is the division of the number of favourable outcomes by the total number of outcomes that is,

Probability of an event = Number of favourable cases Total number of cascs

Determine the probability of getting a red ball by using the formula.
Question Image

Determine the value of x by using the formula.

Probability getting a black ball = Number of black balls in the bag Total number of balls 25 = 20 x 2 x = 5 × 20 x = 50

Therefore, the probability of getting a red ball is

\frac{3}{10}

and the required number of balls is 50.
Hence, the correct option is 1.

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