1MA0 Foundation June 2017 Paper 1 Q24
24 There are 5 girls, 6 boys and some adults in a room.
Jenny selects at random one of these people.
The probability that Jenny selects a girl is \(\frac{1}{3}\)
Work out the probability that Jenny selects an adult. (3)
| Answer | Mark | Notes |
|---|---|---|
| \(\frac{4}{15}\) | 3 | M1 for a method to find the total number of people e.g. \(3 \times 5\) (= 15) or writing \(\frac{5}{15}\) as an equivalent fraction to \(\frac{1}{3}\) M1 (dep) for \(\text{``}15\text{''} - 5 - 6\) (= 4) A1 oe or M1 for a method to find prob (boy) e.g. \(\frac{6}{5} \times \frac{1}{3}\ \left(= \frac{6}{15}\right)\) M1 (dep) for \(1 - \text{``}\frac{6}{15}\text{''} - \frac{1}{3}\) A1 oe or M1 for an expression for the probability of the number of girls in the room e.g. \(\dfrac{5}{5 + 6 + x}\) M1 (dep) for \(\text{``}\dfrac{5}{5 + 6 + x}\text{''} = \dfrac{1}{3}\) or \(x = 4\) A1 oe SC B2 for \(\frac{4}{n}\) where \(n \gt 4\) and \(\ne 15\) |