Mathematics and Numerical Reasoning
What the section tests
Numerical reasoning covers arithmetic with whole numbers, fractions, decimals and percentages, ratio and proportion, averages, simple interest, measurement and unit conversion, basic algebra, and interpretation of tables and simple graphs. Speed and accuracy both count, so mental arithmetic with common fractions and percentages is an advantage.
Traps to watch
Unit mismatches are the most common error: minutes against hours, cents against dollars, grams against kilograms. Percentage questions test whether you find the part, the whole, or the rate; a 20% discount followed by 10% off is not 30% off. Average questions may ask for a missing value, requiring the total. Ratio questions often give a total and ask for one share, so add the ratio parts first. Also read whether an answer must be rounded, and check that the question asks for the total rather than the remainder.
Rule of thumb
Write the given values with units, convert to one unit, then compute. For percentages, use the equation part = rate x whole and fill in the two known values. For multi-step word problems, estimate first so you can spot an implausible answer.
Worked example
A constable earns $2,400 a month and saves 15%. Monthly saving = 0.15 x 2,400 = $360. Annual saving = 360 x 12 = $4,320. A common wrong answer is $360, from stopping at the monthly figure.