Drink preferences by age group in a partly completed two-way table, then a marginal and a conditional probability
Drink preferences by age group in a partly completed two-way table, then a marginal and a conditional probability
4 marks
A café asked \(120\) of its customers whether they prefer tea or coffee. Of the \(55\) customers aged under \(30\), \(38\) chose coffee, and \(41\) of the customers aged \(30\) and over also chose coffee. Some of the results are shown in the table.
| Under \(30\) | \(30\) and over | Total | |
|---|---|---|---|
| Tea | |||
| Coffee | \(38\) | \(41\) | |
| Total | \(55\) | \(120\) |
One of these customers is chosen at random. Find the probability that the customer
- prefers tea;
- prefers coffee, given that the customer is aged \(30\) or over.
[4]
Solution:
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Answer:(a) \(\dfrac{41}{120}\) (b) \(\dfrac{41}{65}\)
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