Higher June 2017 Unit 2 Q16
16. The table below shows the three-day rain forecast for Monday, Tuesday and Wednesday in Eglwyswrw.
| Day | Probability of rain |
|---|---|
| Monday | 80% |
| Tuesday | 80% |
| Wednesday | 80% |
For these three days,
(a) calculate the probability that it will rain on all three days. [2]
(b) calculate the probability that it will rain on exactly 2 consecutive days. [3]
| Scheme | Marks | Comments |
|---|---|---|
| (0.8)3 or equivalent | M1 | Allow 80(%)3 |
| = 0.512 or equivalent | A1 | Fractional answer: 64/125 (ISW) |
| Scheme | Marks | Comments |
|---|---|---|
| 2 × (0.8)2 × 0.2 OR equivalent | M2 | M1 for sight of 0.82 × 0.2 or for sight of 0.128. |
| = 0.256 or equivalent | A1 | Fractional answer: 32/125 (ISW) |