Higher June 2019 Paper 6 Q1
1 A grain of salt weighs \(6.48 \times 10^{-5}\) kg on average.
A packet contains 0.35 kg of salt.
(a) Use this information to calculate the number of grains of salt in the packet. [2]
(b) Explain why your answer to part (a) is unlikely to be the actual number of grains of salt in the packet. [1]
| Answer | Marks | Part marks and guidance | |
|---|---|---|---|
| 5400 or 5401 or 5402 final answer | 2 | M1 for figs 35 ÷ figs 648, soi by figs 540[1…] or for 0.000 064 8 seen | |
| Answer | Marks | Part marks and guidance | |
|---|---|---|---|
| Any reference to average/inexact weight oe [in packet weight or weight of a grain] or recognising that the number of grains of salt must be integer oe | 1 | Condone any mention of average for variation and/or size for weight Mark the best part if no contradiction or wrong statement See appendix | |
Appendix: exemplar responses for Q1(b)
| Response | Comment | Mark |
|---|---|---|
| Because it is a decimal and you can’t have a decimal of a grain of salt. | Reference to requiring integer value | 1 |
| They might have rounded the 0.35kg up. | Equivalent to “figures not exact” | 1 |
| Some grains can be lighter or heavier than this. | “this” is “the average”? | 1 |
| The weight of each grain is an average. | True; mention of average | 1 |
| The weight given is an average weight. | True; mention of average | 1 |
| As it is an average amount of salt. | True; mention of average. Read amount for weight | 1 |
| Some grains of salt may be heavier. | Implies variation | 1 |
| It’s an average | Minimum case | 1 |
| It’s not exact | Minimum case | 1 |
| It’s a decimal | Minimum case | 1 |
| Because it is hard to exactly measure that finite amount consistently. | It may be “hard to measure” but doesn’t say they are not exact. | 0 |
| It’s an estimate because in some packets there will be slightly more or less grains as they are too small to count. | Refers to the number of grains and does not reference the weight of a grain. | 0 |
| There could be a fraction of a grain of salt. | Implies number of grains can be non-integer. | 0 |
| They all weigh the same but could be different sizes | Choice: one incorrect statement and one correct | 0 |