Question

An urn contains 7 white balls and 4 red balls. Draw three balls from the urn without replacement. What is the probability all balls are white?

Answer 1

`7/33`

Explanation:

There are 11 balls altogether, but we are only interested in drawing the white ones. The numbers change each time one ball is removed.
The number of white balls available and the total number of balls drop each time.

`P(WWW) = P(W) xx P(W)xx P(W)`
=`7/11 xx6/10xx5/9`
=`7/33`