Multiple choice

An urn contains 80 blue and 3 yellow balls. Two balls are drawn without replacement. What is the probability that the second ball is yellow, if it is known that the first ball drawn was blue?

  1. 80C3

  2. 83C2

  3. 3/80

  4. 3/82

  5. 3/83

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

If all the 83 balls are considered, then originally there were 80 blue and 3 yellow balls. Since one of the blue ball has already been revealed, now the probability of getting one yellow ball out of 3 yellow and remaining (80 - 1) or 79 blue balls = 3/(3+79) = 3/82