Foundation June 2018 Paper 2 Q13
13 Here is a formula for the amount of water needed to cook rice.
\[w = 1.5r + 0.5\]\(w\) is the number of cups of water needed
\(r\) is the number of cups of rice to be cooked
(a) How many cups of water are needed to cook 7 cups of rice? [2 marks]
(b) How many cups of rice can be cooked with 20 cups of water? [3 marks]
| Answer | Mark | Comments |
|---|---|---|
| \(1.5 \times 7 + 0.5\) or \(10.5 + 0.5\) | M1 | oe |
| 11 | A1 |
Additional guidance
| \(1.5 \times 7 = 10.5\) and \(0.5 \times 7 = 3.5\) and \(10.5 + 3.5 = 14\) | M0A0 |
| \(7 \times 1.5r + 0.5\) | M0A0 |
| \(7 \times 1.5r + 0.5\) and answer \(11r\) | M0A0 |
| \(7 \times 1.5r + 0.5\) and answer 11 (has recovered) | M1A1 |
| Answer | Mark | Comments |
|---|---|---|
| Alternative method 1 | ||
| \(20 - 0.5\) or 19.5 or \(r = \dfrac{w - 0.5}{1.5}\) | M1 | oe |
| their \(19.5 \div 1.5\) | M1dep | oe \((20 - 0.5) \div 1.5\) is M2 |
| 13 | A1 | |
| Alternative method 2 | ||
| 20 – their 11 from part (a) or 9 | M1 | implied by ‘6 extra cups (of rice)’ |
| \(7 +\) (their \(9 \div 1.5\)) or \(7 + 6\) | M1dep | |
| 13 | A1 | |
Additional guidance
| 13 from incorrect working eg rounding \(20 \div 1.5 = 13\) eg scaling 11 and rounding ie \(20 \div 11 \times 7 = 13\) | M0M0A0 |
| Brackets omitted ie \(20 - 0.5 \div 1.5\), unless recovered | M0M0A0 |
| \(1.5 \times 13 + 0.5 = 20\), unless 13 selected | M1M1A0 |
| \(1.5 \times 13 = 19.5\), unless 13 selected | M1M1A0 |
| Trial and improvement, unless answer 13 | M0M0A0 |