Numerical Reasoning and Quantitative Aptitude
What this domain tests
Numerical reasoning tests arithmetic fluency under time pressure: percentages, ratios, averages, rates, work and speed problems, and number series. Some computer-based platforms provide an on-screen calculator; confirm before the test and practise both with and without one.
Core rules and concepts
- Percentage change = (new - old) / old x 100. Distinguish percent from percentage points: a rise from 20% to 25% is 5 percentage points but a 25% increase.
- Ratios: total = sum of parts. If A:B = 3:5 and the total is 64, one part is 8.
- Averages: sum = average x count. Weighted average weights each group by its size.
- Work rate: rates add. If A takes 6 days and B takes 3, together they take 1 / (1/6 + 1/3) = 2 days.
- Speed: distance = speed x time; convert units before dividing.
- Series: check differences, ratios, alternating patterns, and squares or cubes before assuming a single rule.
Worked example
A team of 6 completes 40% of a report in 5 days. How many more days will 10 staff take at the same rate?
6 workers x 5 days = 30 worker-days for 40%. The full job needs 30 / 0.40 = 75 worker-days. Remaining work = 45 worker-days. With 10 staff: 45 / 10 = 4.5 days.
Traps that cost marks
- Answering total days rather than additional days.
- Adding times instead of rates in work problems.
- Rounding early; carry fractions to the final step.
- Mixing units such as minutes and hours, or thousands and millions.
- Forgetting that a discount followed by a rise is not a return to the original price.