The answer
(a) \(FE\) · (b) \(BC\)
PSLE 2025 Paper 1 Question 21 · Verified worked solution by the Genius Plus Academy teaching team
What this question tests
This is Question 21 of the PSLE 2025 Paper 1 Mathematics paper. It tests geometry (properties of shapes), in the Measurement & Geometry strand. It is worth 2 marks. Open your copy of the paper at this question, then follow our full worked solution below.
(a) Parallel lines run in the same direction and never meet: \(FE\) has the same slope on the grid as \(AB\), so \(FE \parallel AB\).
(b) Perpendicular lines meet at \(90^{\circ}\): \(BC\) meets \(CD\) at a right angle, so \(BC \perp CD\).
Answer: (a) \(FE\) · (b) \(BC\)
Same structure, different costume
Change egg tarts to badges, a tank to two tanks, a ring of card to a folded sheet, and a child sees a brand new problem. The lock underneath is the same, and so is the key. Once a student can name the structure, a whole row of questions that look different start to open the same way.
It is also where marks really leak. Across fourteen years of papers, the marks lost in PSLE math leak at the reading far more than at the arithmetic, which is exactly why recognising the structure fixes them. We call this Lock and Key: name the lock, then the key follows.
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One of the 10 question types
The PSLE keeps testing the same 10 structures. Our PSLE Math Intensive trains the Lock and Key reflex across all ten, with 158 curated questions over two days.
It is a geometry (properties of shapes) question from the Measurement & Geometry strand, worth 2 marks.
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