Edexcel GCSE Maths (1MA1), Higher tier · Geometry and measures
Practise Vectors. 1 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
OPR and OQS are straight lines. \(\overrightarrow{OP} = \mathbf{s}\) and \(\overrightarrow{OQ} = \mathbf{t}\). \(\overrightarrow{OR} = 3\mathbf{s}\) and \(\overrightarrow{OS} = 3\mathbf{t}\). Diagram NOT accurately drawn
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(a) Prove that PQSR is a trapezium.[3]
(b) Write down the ratio of the length of PQ to the length of RS.[1]
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(a)Answer: \(\overrightarrow{PQ} = \mathbf{t} - \mathbf{s}\) and \(\overrightarrow{RS} = 3\mathbf{t} - 3\mathbf{s} = 3(\mathbf{t} - \mathbf{s})\), so \(\overrightarrow{RS} = 3\overrightarrow{PQ}\): PQ is parallel to RS and 3 times as long, so PQSR is a trapezium.
M1 for \(\overrightarrow{PQ} = \mathbf{t} - \mathbf{s}\) or \(\overrightarrow{RS} = 3\mathbf{t} - 3\mathbf{s}\)
M1 for \(\overrightarrow{RS} = 3(\mathbf{t} - \mathbf{s})\) or \(3\overrightarrow{PQ}\)
C1 for a complete proof: \(\overrightarrow{RS}\) is a multiple of \(\overrightarrow{PQ}\), so PQ is parallel to RS, and they are not equal in length, so PQSR is a trapezium
Worked solution: \(\overrightarrow{PQ} = \overrightarrow{PO} + \overrightarrow{OQ} = -\mathbf{s} + \mathbf{t} = \mathbf{t} - \mathbf{s}\) \(\overrightarrow{RS} = \overrightarrow{RO} + \overrightarrow{OS} = -3\mathbf{s} + 3\mathbf{t} = 3(\mathbf{t} - \mathbf{s}) = 3\overrightarrow{PQ}\) So RS is parallel to PQ and 3 times as long: PQSR has one pair of parallel sides of different lengths, so it is a trapezium.
(b)Answer: 1 : 3
B1 for 1 : 3 oe
Worked solution: \(\overrightarrow{RS} = 3\overrightarrow{PQ}\), so RS is 3 times as long as PQ: PQ : RS = 1 : 3.