WASSCE Economics · Paper 1 style

Demand

One sample question with the full working. 11 more in the app, with instant feedback and repair sessions for the traps below.

When the price of a commodity changes from ₦20 to ₦25, the quantity demanded changes from 50 units to 45 units. Calculate the price elasticity of demand (absolute value).

A0.40
B0.56
C2.50
D1.00

Show the answer and working

Answer: A

%ΔQ = (45 − 50)/50 × 100 = −10%; %ΔP = (25 − 20)/20 × 100 = +25%. |PED| = 10/25 = 0.40 (inelastic).

Trap B Uses the wrong base in a ratio: Percentage change = change ÷ ORIGINAL value. Unemployment rate = unemployed ÷ LABOUR FORCE (employed + unemployed). Write the base before dividing.

Trap C Turns the formula upside down: Learn the formula with its meaning: elasticity = responsiveness of QUANTITY, so %ΔQ is on top; k = 1/MPS = 1/(1 − MPC).

Trap D Stops at a different economic quantity: Underline what the question asks for and check the final number is THAT quantity, not a step on the way.

Traps in Demand

Uses the wrong base in a ratio
Percentage change = change ÷ ORIGINAL value. Unemployment rate = unemployed ÷ LABOUR FORCE (employed + unemployed). Write the base before dividing.
Turns the formula upside down
Learn the formula with its meaning: elasticity = responsiveness of QUANTITY, so %ΔQ is on top; k = 1/MPS = 1/(1 − MPC).
Stops at a different economic quantity
Underline what the question asks for and check the final number is THAT quantity, not a step on the way.
Reverses the direction of the effect
Trace the chain step by step (e.g. buying securities → banks gain cash → money supply rises) and check the sign at every link.
Confuses a movement along a curve with a shift
Own price changes → movement ALONG the curve. Any other factor (income, tastes, price of related goods, costs) → SHIFT of the curve.
Picks a closely related concept
Learn related terms as contrasting pairs with one-line definitions, and identify which one the stem describes.
Applies the rule for the opposite case
Before answering, name the case in the stem (inelastic? price floor ABOVE equilibrium? point INSIDE the PPC?) and recall the rule for that case only.
Picks another type in the same classification
Learn each classification as a table of types with one defining feature each (monopoly: one seller; monopsony: one buyer; command economy: central planning).
Gives only part of the answer
List every component in the definition (GDP = C + I + G + (X − M)) and tick them off before answering.
Uses the everyday meaning of a term
Economic terms have precise definitions. Recall the textbook definition before matching.
Chooses a true but irrelevant statement
Re-read the question's key term and test each option against it, not against whether it is true in general.
Over-generalises a rule
Economic laws hold 'other things being equal' and within limits. Be suspicious of options with always/never/all.
Errors in finding market equilibrium
At equilibrium Qd = Qs. Solve for P, then substitute to find Q. If price is above equilibrium, Qs > Qd → surplus (excess supply); below equilibrium, Qd > Qs → shortage (excess demand).

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