Higher June 2019 Paper 6 Q6
6 A bag contains some counters.
- There are 300 counters in the bag.
- There are only red, white and blue counters in the bag.
- The probability of picking a blue counter is \(\frac{23}{50}\).
- The ratio of red counters to white counters is 2 : 1.
Calculate the number of red counters in the bag. [4]
| Answer | Marks | Part marks and guidance | |
|---|---|---|---|
| 108 nfww | 4 | B3 for \(\dfrac{108}{300}\) OR M3 for \(\left(300 - \dfrac{23}{50} \times 300\right) \div 3 \times 2\) oe or M2 for \(300 - \dfrac{23}{50} \times 300\) soi 162 or M1 for \(\dfrac{23}{50} \times 300\) oe soi 138 Alternative method M1 for [p(white or red) =] \(1 - \dfrac{23}{50}\) soi \(\dfrac{27}{50}\) M1 for their \(\dfrac{27}{[50]} \div 3 \times 2\) soi \(\dfrac{18}{[50]}\) M1 for their 18 × 6 or their \(\dfrac{18}{50} \times 300\) | May use percentages or decimals for M marks May use 23 : 18 : 9 for M2 |