CAIE IGCSE Mathematics Core C8.3 Probability of Combined Events Topic Practice

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Covered syllabus points

C8.3.1 Calculate the probability of combined events using, where appropriate:

Question 1

[Maximum number: 4]

There are 2 sets of traffic lights on Li's journey to work.
The probability he stops at the first set of traffic lights is 0.4 .
The probability he stops at the second set of traffic lights is 0.7 .

First set of traffic lights

Figure for Question 1 — CAIE IGCSE Mathematics Core

Question (a)

(a)

Complete the tree diagram.

Second set of traffic lights

Figure for Question (a) — CAIE IGCSE Mathematics Core
[ 2 ]

Question (b)

(b)

Work out the probability that Li does not stop at both sets of traffic lights.

[ 2 ]

Question 2

[Maximum number: 1]
Figure for Question 2 — CAIE IGCSE Mathematics Core

E={students in a year group}E=\{\text{students in a year group}\}H={students who study History}H=\{\text{students who study History}\}G={students who study Geography}G=\{\text{students who study Geography}\}
80 students are in the year group.
40 students study History.

A student is chosen at random.

Work out the probability that the student does not study History and does not study Geography.

Question 3

[Maximum number: 5]

A box contains 10 counters.
The counters are either red or green.
The ratio red counters: green counters =1: 4.
Shareen picks a counter at random, notes its colour and puts it back in the box.
She then picks a second counter at random.

Figure for Question 3 — CAIE IGCSE Mathematics Core

Question (a)

(a)

Complete the tree diagram.

[ 3 ]

Question (b)

(b)

Find the probability that both counters are green.

[ 2 ]
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