Numerical Reasoning: Set Up Before You Compute
Set up the problem before you compute
Numerical reasoning items are usually short word problems: percentages and percent change, ratios and proportions, averages, rates (units per hour, miles per gallon), simple unit conversions, and number sequences. The arithmetic is rarely hard; the difficulty is choosing the right operation and the right base.
Traps to expect:
- Percent of versus percent more than. A 20% increase followed by a 20% decrease does not return you to the starting value.
- Wrong base. Percent of the original price and percent of the sale price give different answers.
- Unit mismatch. Minutes mixed with hours, cents with dollars, ounces with pounds. Convert first, then calculate.
- Early rounding. Round only at the end; rounding mid-way can push your result off the answer list.
- Sequence rules that fit twice. Confirm your rule against at least two consecutive steps.
Worked example. Three machines produce 900 units in 6 hours. How many units does one machine produce per hour? Total machine-hours = 3 × 6 = 18. Rate = 900 ÷ 18 = 50 units per machine-hour. Answer: 50.
Rule of thumb: write the units into the equation (units ÷ machine-hour), estimate the answer to one significant figure before computing, and sanity-check the result. If the question asks for hours and you get 300, you divided where you should have multiplied.