Higher June 2018 Paper 6 Q7
7 Edsel has four number cards.
Sharon has three number cards.
\(u\) represents a number that Sharon knows.
Edsel and Sharon each pick one of their cards at random.
They calculate the difference between the numbers on their cards.
This is their sample space.
| Edsel | |||||
|---|---|---|---|---|---|
| 3 | 8 | 9 | 12 | ||
| Sharon | 6 | 3 | 2 | 3 | 6 |
| 11 | 8 | 3 | 2 | 1 | |
| \(u\) | 11 | 6 | \(r\) | \(t\) | |
Work out the values of \(r\) and \(t\). [4]
| Answer | Marks | Part marks and guidance | |
|---|---|---|---|
| \(r = 5\) \(t = 2\) | 4 | M2 for \(u = 14\), may be seen in table A1 for \(r = 5\) or \(t = 2\) OR | If no credit-worthy working B2 for \(r = 5\) B2 for \(t = 2\) |
| M1 for \(\pm(u - 3) = 11\) oe soi by \(u = -8\) or \(\pm(u - 8) = 6\) oe soi by \(u = 2\) A1FT for \(r = 17\) and \(t = 20\) following \(u = -8\) or \(r = 7\) and \(t = 10\) following \(u = 2\) | FT only from a partially correct value for \(u\) (ie. −8 or 2) | ||