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2.3 Probability

Question 8

A box contains $n\,$ petrol key fobs and 6 diesel key fobs, where $n\,$ is a positive integer. A fob is selected at random, replaced, and then a second fob is selected.

The probability that both fobs selected are diesel is $14\displaystyle \frac{1}{4}$ .

Show that $n^2 + 12n - 108 = 0$ .

[3]

Hence find the value of $n$ .

[2]

Find the probability that the two fobs taken are of different types.

[2]

Markscheme

2.3 Probability Questions

A Level
Maths
2.3 Probability

36 exam-style questions on WJEC A Level Maths 2.3 Probability, covering 2.3.1 Probability and 2.3.2 Probability. Each one has a worked solution and a mark scheme showing where the marks go.

2.3 Probability

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2.3 Probability

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Question 8

A box contains $n\,$ petrol key fobs and 6 diesel key fobs, where $n\,$ is a positive integer. A fob is selected at random, replaced, and then a second fob is selected.

The probability that both fobs selected are diesel is $14\displaystyle \frac{1}{4}$ .

Show that $n^2 + 12n - 108 = 0$ .

[3]

Hence find the value of $n$ .

[2]

Find the probability that the two fobs taken are of different types.

[2]

Markscheme

2.3 Probability Questions

A Level
Maths
2.3 Probability

36 exam-style questions on WJEC A Level Maths 2.3 Probability, covering 2.3.1 Probability and 2.3.2 Probability. Each one has a worked solution and a mark scheme showing where the marks go.