Question

An urn contains one black ball and one green ball. A second urn contains one white and one green ball. One ball is drawn at random from each urn. What is the probability that both balls are of same colour?

• A. $1/2$
• B. $1/3$
• C. $1/4$
• D. $2/3$

Answer 1

The correct option is C $1/4$

Given:

Urn 1: 1 black and 1 green ball = 2 balls in total

Urn 2: 1 white and 1 green ball = 2 balls in total

One ball is drawn from each mean two balls in total are drawn.

To find:

The probability that both balls are of the same colour

The same colour ball can be possible only if we get 1 green from urn 1 and 1 green from the urn 2.

Hence, the probability that both balls are of the same colour = $\frac{{}^1{C}_1}{{}^2{C}_1}\times \frac{{}^1{C}_1}{{}^2{C}_1}=\frac{1}{4}$