Further Mathematics Paper 2, August/Sptember. 2018

Question 13

 

One out of every 3 bolts produced by a machine is defective. If 4 of the bolts produced by the machine are selected at random, find the probability that:

  1. exactly 2 are defective;
  2. at least 1 is defective;
  3. at most are defective.

Observation