CAIE S1 2024 June — Question 2

Exam BoardCAIE
ModuleS1 (Statistics 1)
Year2024
SessionJune
TopicConditional Probability
TypeConditional probability with given score/outcome

2 Seva has a coin which is biased so that when it is thrown the probability of obtaining a head is \(\frac { 1 } { 3 }\). He also has a bag containing 4 red marbles and 5 blue marbles. Seva throws the coin. If he obtains a head, he selects one marble from the bag at random. If he obtains a tail, he selects two marbles from the bag at random and without replacement.
  1. Find the probability that Seva selects at least one red marble.
  2. Find the probability that Seva obtains a head given that he selects no red marbles.