CIE iGCSE Maths C8.3 Probability of combined events Exam Style Practice Questions- Paper 1

Question

Geetha has a box of toys.

She picks a toy at random from the box.

The probability that she picks a wooden toy is 0.6.

(a) Work out the probability that she does not pick a wooden toy.

(b) The box contains three types of toys, wooden, plastic or metal.

Complete the table.

▶️ Answer/Explanation

Solution

(a) Ans: 0.4

Since the probability of picking a wooden toy is \(0.6\), the probability of not picking a wooden toy is \(1 – 0.6 = 0.4\).

(b)

Given the probabilities must sum to 1, the missing probability for plastic toys is \(1 – (0.6 + 0.25) = 0.15\).

The completed table is:

Question

A bag contains 50 counters.
10 of the counters are red.
One of the counters is taken from the bag at random.

(a) Draw an arrow (↓) on the scale to show the probability that this counter is red.

(b) Find the probability that the counter is not red.

▶️ Answer/Explanation

Solution

(a) Ans: Arrow at 0.2

Probability of red = Number of red counters ÷ Total counters = 10/50 = 0.2.

Mark the arrow at 0.2 on the scale since P(red) = 0.2.

(b) Ans: 0.8

P(not red) = 1 – P(red) = 1 – 0.2 = 0.8.

Alternatively: (50-10)/50 = 40/50 = 0.8.

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