Number and Quantity in Everyday Contexts
What you need to understand
This domain tests whether you can work confidently with the numbers that turn up in daily life: whole numbers, decimals, fractions, percentages, ratios, rates and simple proportion. You should be able to round sensibly, estimate before calculating, convert between fractions, decimals and percentages, and use place value to judge whether an answer is reasonable. Order of operations matters, and so does the ability to work with negative numbers in contexts such as temperature or bank balances.
Traps to watch for
- Rounding too early. Round only at the end of a calculation, then round the final answer as asked.
- Percentage increase versus percentage of. A 20% discount is not the same as "20% of the original price added on".
- Mixing units inside a ratio. Convert to the same unit before simplifying.
- Direction of comparison. "How many times larger" is a division, not a subtraction.
- Estimation questions often reward a sensible approximate answer, not an exact one, so check the size of your result.
Worked example
A jacket costs $80 and is reduced by 15%, then a further 10% is taken off the reduced price. What is the final price?
First discount: 15% of $80 = $12, so the price becomes $68. Second discount: 10% of $68 = $6.80, so the final price is $61.20. Notice the second discount is taken from $68, not $80 - a common trap is to add the percentages and take 25% off $80, which gives $60 and is wrong.
Rule of thumb
Estimate first, calculate carefully, then ask: does this answer make sense in the context?