GCSE Maths revision · Higher: probability and statistics
is the probability of given that has happened. Only look at the outcomes where happened: .
Watch out The total changes to the group you are given.
A theatre sells 48 tickets. Of these, 18 are child tickets. Twelve of the child tickets and 21 of the adult tickets are for the evening performance. One of the evening tickets is selected at random. Work out the probability that it is a child ticket. Give a fraction in its simplest form.
Answer 4/11
At a club, 80 members are surveyed. There are 46 members who cycle to the club, including 18 who also swim. Of the members who do not cycle, 12 swim. One member who does not swim is chosen at random. Work out the probability that this member cycles. Give a fraction in its simplest form.
Box A has 3 red and 2 blue counters. Box B has 1 red and 4 blue counters. A box is chosen with probability 2/3 for A and 1/3 for B, then one counter is chosen randomly from that box.
(a) Find the probability of a red counter.
(b) Given that the counter is red, find the probability it came from A.
Three sensors A, B and C work independently. The probabilities that A and B work are 0.8 and 0.6 respectively. An alarm operates if at least two sensors work. The probability that the alarm operates is 0.7. Given that the alarm operates, work out the probability that all three sensors work. Give a fraction in its simplest form. You must show your working.
46 official questions in 44 papers since 2017. The latest:
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