4MA0 Higher June 2017 Paper 4R Q21
21

Diagram NOT accurately drawn
\(OAB\) is a triangle.
\(X\) is the midpoint of \(OA\) and \(W\) is the midpoint of \(OB\).
\(Y\) is the point on \(AW\) such that \(AY : YW = 2 : 1\)
\(\overrightarrow{OX} = 3\mathbf{a}\) and \(\overrightarrow{OW} = 3\mathbf{b}\)
| Scheme | Marks |
|---|---|
| (i) Answer: \(3\mathbf{b} - 6\mathbf{a}\) | B1 |
| (ii) Answer: \(2\mathbf{b} - 4\mathbf{a}\) | B1ft |
| (iii) Answer: \(6\mathbf{b} - 3\mathbf{a}\) | B1 |
| (3) |
Notes
B1: Oe
Need not be simplified
Mark the final answer
B1: oe
Need not be simplified
Mark the final answer
| Scheme | Marks |
|---|---|
| Eg \(\overrightarrow{XY} = 2\mathbf{b} - \mathbf{a}\) oe or \(\overrightarrow{YB} = 4\mathbf{b} - 2\mathbf{a}\) | M1 |
| shown | A1 |
| (2) | |
| (5 marks) |
Notes
M1: Work out \(\overrightarrow{XY}\) or \(\overrightarrow{YX}\) or \(\overrightarrow{YB}\) or \(\overrightarrow{BY}\)
A1: Dep on M1
Correct conclusion from correct simplified vectors
Eg \(\overrightarrow{XB} = 3\overrightarrow{XY}\) or \(\overrightarrow{YB} = 2\overrightarrow{XY}\) or \(\overrightarrow{XB} = 1.5\overrightarrow{YB}\)
or \(XB\) and \(XY\) are parallel
or \(YB\) and \(XY\) are parallel
or \(XB\) and \(YB\) are parallel