Edexcel IGCSE Math A 6.3.HD probability problem solving

Practise probability problem-solving by identifying the relevant model, forming the calculation and solving for the requested count or chance.

Exam points

Find an estimated probability from a restricted group or interval in the data.
Work backwards from probability information to find a missing number of counters.
Calculate an exact probability for repeated events such as winning two of three races.

[Maximum number: 3]

Emilie takes part in two races.
The probability that she wins the first race is 0.7
The probability that she wins the second race is 0.4
The outcomes of the two races are independent.

Work out the probability that Emilie will win exactly two of the three races.

Exactly two wins in three races:
$0.7\times0.4\times(1-0.6)=0.112$ $0.54\times0.3=0.162$ 0.112+0.162=0.274
Final answer:
0.274
Equivalent answer $\frac{137}{500}$ accepted.

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6.3.HD Probability to simple problems question 1