CAIE S1 2019 November — Question 2

Exam BoardCAIE
ModuleS1 (Statistics 1)
Year2019
SessionNovember
TopicConditional Probability
TypeFinding unknown probability from total probability

2 Benju cycles to work each morning and he has two possible routes. He chooses the hilly route with probability 0.4 and the busy route with probability 0.6 . If he chooses the hilly route, the probability that he will be late for work is \(x\) and if he chooses the busy route the probability that he will be late for work is \(2 x\). The probability that Benju is late for work on any day is 0.36 .
  1. Show that \(x = 0.225\).
  2. Given that Benju is not late for work, find the probability that he chooses the hilly route.