Higher November 2017 Paper 1 Q25
25 15 machines work at the same rate.
Together, the 15 machines can complete an order in 8 hours.
3 of the machines break down after working for 6 hours.
The other machines carry on working until the order is complete.
In total, how many hours does each of the other machines work? [3 marks]
| Answer | Mark | Comments |
|---|---|---|
| Alternative method 1 | ||
| \(15 \times 8\) or 120 or \(3 \times 6\) or 18 | M1 | oe total number of hours needed oe total number of hours worked by the 3 machines |
| \(15 \times 8 - 3 \times 6\) or 102 | M1dep | oe total number of hours worked by the other 12 machines |
| 8.5 | A1 | |
| Alternative method 2 | ||
| \(3 \times (8 - 6)\) or \(3 \times 2\) or 6 | M1 | oe total number of hours not worked by the three machines |
| their \(6 \div 12\) or 0.5 | M1dep | oe that number divided by the other 12 machines |
| 8.5 | A1 | |
| Alternative method 3 | ||
| \(15 \times 8\) or 120 or \(15 \times 6\) or 90 | M1 | oe total number of hours needed oe total number of hours worked in the first 6 hours |
| \(\dfrac{15 \times 8 - 15 \times 6}{12}\) or 2.5 | M1dep | oe number of remaining hours divided by the other 12 machines |
| 8.5 | A1 | |
Additional guidance
Note that \(15 \div 6\) is not a correct method to get 2.5 (unless simplified from \(30 \div 12\)), so does not score