Quantitative Literacy: Rates, Percentages and Data Sense
What this section tests
Quantitative Literacy checks whether you can use numbers in context rather than manipulate symbols. Expect percentages and percentage change, ratio and proportion, rates per unit, scaling and unit conversion, reading tables and graphs accurately, averages (mean, median, mode), elementary probability, and simple financial reasoning such as interest and discounts. The emphasis is on interpreting a real situation and choosing the right operation, not on lengthy algebra.
Traps that appear
- Percent of versus percent change: "20% of 300" is 60; "increased by 20%" from 300 gives 360.
- Adding percentages: successive changes do not add and do not cancel. A rise then an equal fall leaves you below the start.
- Unit mismatch: minutes versus hours, cents versus rand, per month versus per year.
- Graph axes: a y-axis that does not start at zero exaggerates differences; check scale and labels before reading a trend.
- Mean versus median: one outlier drags the mean but barely moves the median.
- Rate versus total: a bigger total does not mean a bigger rate.
Rule of thumb
Write the units next to every number, estimate a rough answer first, then compute. If your calculation lands far from the estimate, the error is usually a misplaced decimal or an inverted ratio.
Worked example
A jacket costs R800. Its price rises 20%, then falls 20% in a sale. R800 × 1,20 = R960; R960 × 0,80 = R768. The final price is R768, not R800, because the second 20% is taken from the larger amount. In general, a +p% followed by −p% leaves the original multiplied by (1 + p)(1 − p) = 1 − p², a net loss.