Question

Find the probability of getting both red balls, when from a bag containing 5 red and 4 black balls, two balls are drawn, without replacement

Answer 1

There are 9 balls i.e. 5 red and 4 black.

When balls are drawn without replacement, first ball can be drawn in 9 ways.

After that second ball can be drawn in 8

 ∴ n(S) = 9 × 8 = 72

First red ball can be drawn in 5 ways

∵ ball is not replaced, second red ball can be drawn in 4 ways

∴ two red balls can be drawn in 5 × 4 = 20 ways

∴ the required probability = `20/72` = `5/18`