Foundation November 2020 Paper 3 Q23
23 The probability that Adam cycles to school or walks to school depends on the weather.
- On any day, the probability that the weather is wet is 0.4.
- When the weather is wet the probability that he cycles to school is 0.3.
- When the weather is dry the probability that he cycles to school is 0.8.
The information is shown on this tree diagram.
Work out the probability that
(a) it is dry and Adam walks to school, [2]
(b) Adam cycles to school. [3]
| Answer | Marks | Part marks and guidance | |
|---|---|---|---|
| 0.12 oe isw | 2 | M1 for \(0.6 \times 0.2\) | Ignore attempts to change form once correct answer seen. Accept 12% or \(\dfrac{12}{100}\) or equivalent fraction |
| Answer | Marks | Part marks and guidance | |
|---|---|---|---|
| 0.6 oe isw | 3 | M2 for \(0.4 \times 0.3 + 0.6 \times 0.8\) or M1 for \(0.4 \times 0.3\) or \(0.6 \times 0.8\) | Accept 60% or equivalent fraction Ignore attempts to change form once correct answer seen. 0.12 could come from (a) so calculation must be seen for M2 May be implied by 0.48 |