Mathematics and Data Interpretation
What the test measures
Expect arithmetic and basic algebra applied to work situations: percentages, ratios and proportions, averages, rates such as speed and distance, unit conversions, and reading information from tables, charts, and graphs. Data-interpretation items ask you to compare values, spot trends, or compute a change from a displayed figure.
Traps that show up
- Percent of vs. percent change. Going from 40 to 50 is a 10-unit increase, which is a 25% increase - not a 10% one.
- Average of averages. You cannot average two group averages unless the groups are the same size; total the values first.
- Unit mismatches. Minutes against hours, or miles against feet, are the most common setup for a wrong answer.
- Graph scales. Check the axis labels and whether the scale starts at zero before judging a trend.
- Early rounding. Round at the end; rounding mid-calculation can shift the answer off the choices.
- Answering the wrong quantity. Confirm whether the question asks for the total, the difference, or the rate.
Rule of thumb
Write the units next to every number and cancel them before computing. If the units do not come out to what the question asks for, the setup is wrong regardless of the arithmetic.
Worked example
A patrol covers 45 miles in 40 minutes. Convert first: 40 minutes = 2/3 hour, so speed is 45 ÷ (2/3) = 67.5 mph. Forgetting the conversion gives 1.125, an answer that appears among the choices and is wrong.