Foundation June 2023 Unit 2 Q10
10. In this question, you will be assessed on the quality of your organisation, communication and accuracy in writing.
Steve has a bag containing 10 discs.
Some of the discs are red. The others are blue.
If a disc is selected at random, the probability of selecting a red disc is \(\dfrac{2}{5}\).
10 more blue discs are added to Steve’s bag.
He now selects one disc at random.
What is the probability that the disc Steve selects is red?
You must show all your working. [3 + 2 OCW]
| Scheme | Marks | Comments |
|---|---|---|
| (Number of red discs = 2/5 × 10 =) 4 | B1 | Allow 4/10 or ‘4 out of 10’ or (number of blue discs = 3/5 x 10 =) 6 |
| (Total number of discs = 10 + 10 =) 20 | B1 | May be seen in the denominator of their answer. Implied by number of red discs = 4 AND number of blue discs = 16. F.T. ‘their number of red discs’. |
| (Probability of a red disc =) \(\dfrac{4}{20}\) ISW | B1 | F.T. \(\dfrac{\underline{\text{‘their number of red discs’}}}{20}\) provided < 1. Award B1 B1 B1 for an unsupported final answer of 4/20 or equivalent. |
| 10. Organisation and Communication | OC1 | For OC1, candidates will be expected to:
|
| Accuracy of writing | W1 | For W1, candidates will be expected to:
|
Notes
The alternative method is printed between the main method and the OC1/W1 rows.
Alternative method
| Scheme | Marks | Comments |
|---|---|---|
| (Probability of a red disc =) 2/5 ÷ 2 | M2 | |
| 2/10 ISW | A1 |