1MA0 Higher June 2017 Paper 1 Q9
9 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 \(\dfrac{1}{3}\)
Work out the probability that Jenny selects an adult. (3)
| Answer | Mark | Notes |
|---|---|---|
| \(\dfrac{4}{15}\) | 3 | M1 for a method to find the total number of people eg \(3 \times 5\) (= 15) or \(\dfrac{5}{15} = \dfrac{1}{3}\) M1 (dep) for \(\text{``}15\text{''} - 5 - 6\) (= 4) A1 oe OR M1 for a method to find prob (boy) eg \(\dfrac{6}{5} \times \dfrac{1}{3}\left(= \dfrac{6}{15}\right)\) M1 (dep) for \(1 - \text{``}\dfrac{6}{15}\text{''} - \dfrac{1}{3}\) A1 oe OR M1 for an expression for the number of adults eg \(\dfrac{5}{5 + 6 + x}\) M1 (dep) for \(\text{``}\dfrac{5}{5 + 6 + x}\text{''} = \dfrac{1}{3}\) or \(x = 4\) A1 oe SC: B2 for \(\dfrac{4}{n}\) where \(n \gt 4\), \(n \neq 15\) |