WASSCE Core Mathematics · Paper 1 style

Coordinate geometry

One sample question with the full working. 16 more in the app, with instant feedback and repair sessions for the traps below.

Find the equation of the line through (2, 3) that is perpendicular to y = 2x + 1.

Ay = −½x + 4
By = 2x − 1
Cy = ½x + 2
Dy = −2x + 7

Show the answer and working

Answer: A

m = −1/2; y − 3 = −½(x − 2) → y = −½x + 4.

Trap B Inverts or omits part of the gradient formula: Gradient = rise ÷ run = (y₂ − y₁)/(x₂ − x₁). y goes on TOP ("y is high").

Trap C Sign slip when moving or multiplying terms: Moving a term across "=" means doing the opposite operation to BOTH sides. And (−)×(−) = (+). Write each step on a new line; circle every minus sign before you expand.

Trap D Incomplete inverse operations: Undo operations in REVERSE order, one at a time, to the whole of each side. Make a list: what was done to x? Undo the last one first. Check by substituting back.

Traps in Coordinate geometry

Inverts or omits part of the gradient formula
Gradient = rise ÷ run = (y₂ − y₁)/(x₂ − x₁). y goes on TOP ("y is high").
Sign slip when moving or multiplying terms
Moving a term across "=" means doing the opposite operation to BOTH sides. And (−)×(−) = (+). Write each step on a new line; circle every minus sign before you expand.
Incomplete inverse operations
Undo operations in REVERSE order, one at a time, to the whole of each side. Make a list: what was done to x? Undo the last one first. Check by substituting back.
Stops one step short of the answer
Before writing the answer, re-read the question's last words (each angle? neither? Ama's share? variance?). Ask: is my number that thing, or a stage on the way to it?
Swaps two things that must stay in order
Keep order explicit: (x, y); 'bearing of Q from P' starts at P; in p → q the condition comes first. Label each part before you write the answer.
Midpoint formula slips
The midpoint is the AVERAGE of the ends: ((x₁+x₂)/2, (y₁+y₂)/2). Sketch: it must lie between the two points.
Inverts a relationship
Say the rule with its direction (angle at centre = TWICE the angle at the circumference; (x − 1) = 0 gives x = +1). Check your answer against a simple case.
Uses only part of the information
Tick off every number and every condition in the stem as you use it. If one is unticked at the end, the answer is incomplete.
Calculates a different quantity
Name the quantity and its unit before you start (remainder; horizontal distance; cm²). After calculating, check your number is that quantity and not a neighbour.
Mixes up the roles of the quantities
Label each symbol with its meaning (a = first term, d = common difference; in y = mx + c, m = gradient, c = intercept) before substituting.
Applies the rule for a different situation
Identify the situation first (angle at centre? opposite angles of a cyclic quadrilateral? reverse bearing?) and write the rule that belongs to it before calculating.

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