Mathematics 4024 · O Level · Probability of combined events

Probability of combined events — practice question

Mia has 25 shapes altogether. She sorts them into groups according to their properties. The table gives the number of shapes in each group.
(a)[2]

Mia chooses one triangle at random, records its properties and puts it back. Find the probability that it has line symmetry.

(b)[2]

Mia chooses one of the 25 shapes at random, notes its properties and puts it back. She then chooses a second shape at random, notes its properties and puts it back. Find the probability that both shapes are quadrilaterals.

(c)[3]

Mia picks three of the 25 shapes at random without replacement. Find the probability that just one of the shapes is a triangle with line symmetry.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: The probability is $\dfrac{4}{9}$.

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