Higher November 2023 Paper 1 Q18
18 Spinner A and spinner B are each spun once.
The probability that spinner A lands on red is \(\dfrac{1}{4}\)
The probability that both spinner A and spinner B land on red is \(\dfrac{1}{24}\)
Work out the probability that one spinner lands on red and the other spinner does not land on red. (4)
| Answer | Mark | Mark scheme |
|---|---|---|
| \(\dfrac{1}{3}\) | P1 | for start of process to find the probability of spinner B landing on red eg \(\dfrac{1}{4}x = \dfrac{1}{24}\) oe or \(\dfrac{1}{24} \div \dfrac{1}{4}\) or \(x = \dfrac{1}{6}\) |
| P1 | for process to find probability of one red and one not red eg \(\dfrac{1}{4} \times \left(1 - \text{``}\dfrac{1}{6}\text{''}\right) \left(= \dfrac{5}{24}\right)\) or \(\left(1 - \dfrac{1}{4}\right) \times \text{``}\dfrac{1}{6}\text{''} \left(= \dfrac{3}{24}\right)\) or process to find probability of both not red, eg \(\left(1 - \text{``}\dfrac{1}{4}\text{''}\right) \times \left(1 - \text{``}\dfrac{1}{6}\text{''}\right) \left(= \dfrac{15}{24}\right)\) | |
| P1 | for a complete process to find the required probability eg \(\text{``}\dfrac{5}{24}\text{''} + \text{``}\dfrac{3}{24}\text{''}\) or \(1 - \dfrac{1}{24} - \text{``}\dfrac{15}{24}\text{''}\) | |
| A1 | oe |