Higher November 2017 Unit 2 Q13
13. A bag contains 5 red counters and 5 blue counters.
Three counters are drawn at random from the bag at the same time.
Calculate the probability that the three counters will be the same colour. [3]
| Scheme | Marks | Comments |
|---|---|---|
| \(2 \times \frac{5}{10} \times \frac{4}{9} \times \frac{3}{8}\) | M2 | M1 for sight of \(\frac{5}{10} \times \frac{4}{9} \times \frac{3}{8}\) |
| \(= \frac{120}{720}\) or equivalent \(\left(\frac{1}{6}\right)\) | A1 | CAO. Mark final answer. SC1 for an answer of ¼ or 0.25 from the use of calculating ‘with replacement’. |