Paper 3 - Numerical Ability Test
Paper 3 (Numerical Ability) tests arithmetic reasoning rather than advanced mathematics. Expect operations with whole numbers, fractions, decimals and percentages; ratio and proportion; averages; simple interest, profit, loss and discount; elementary algebra; measurement and geometry; and interpretation of tables and graphs. Accuracy under time pressure matters more than clever methods.
Rules that carry most marks
- Order of operations: brackets, orders/powers, division and multiplication (left to right), then addition and subtraction.
- Percentage change = (new − old) ÷ old × 100. A fall from 80 to 60 is a 25% decrease, not 20%.
- Successive percentages do not add: apply each to the new base.
- Ratio: to share an amount in a ratio, add the parts, divide the amount by the total number of parts, then multiply.
- Average = total ÷ number of items; find a missing value by working backwards from the total.
- Geometry: rectangle area = l × w; triangle = ½ × base × height; circle = πr²; box volume = l × w × h.
Worked example
A jacket costs N$480. It is reduced by 15%, then the sale price is reduced by a further 10%. What is the final price? First discount: 480 × 0.85 = N$408. The second discount applies to 408, not 480: 408 × 0.90 = N$367.20. A common wrong answer is 480 × 0.75 = N$360, which wrongly adds the percentages.
Traps
- Adding percentages instead of compounding them.
- Mixing units (minutes with hours, cents with dollars) before calculating.
- Rounding at each step instead of at the end.
- Reading "how many more" as "how many times".
- Percentage points versus percent: 5% to 7% is a 2 percentage-point rise but a 40% increase.
Check your answer against the size you expected.