CaseClimbBefore you reach a case interview, many consulting firms screen applicants with a timed online test. Formats differ from firm to firm and change over time, so check what the firm tells applicants this cycle. Numerical reasoning tests do share a recognisable core: multiple-choice questions, a hard clock, and numbers you have to read, compare and calculate at speed. Some allow a calculator and some don't, so unless the firm says otherwise, prepare to do a lot by hand or in your head.
These tests matter because they mirror client work. On an engagement you run fast calculations in your head several times a day while the assumptions change under you: the client asks "what if volumes are 10% lower?" or "what if we raise the price by 5%?", and you need a sound answer in seconds rather than after a spreadsheet. Speed and accuracy with numbers under time pressure, while you keep the bigger picture in mind, are a core part of the job (and one of the five skills a case interview scores), which is a big reason firms check them early.
What they test
- Percentages and percentage changes, including chained changes.
- Ratios, proportions and shares of a total.
- Growth rates and simple compound growth.
- Reading tables, charts and other exhibits.
- Rates and unit conversions: per hour, per unit, per customer.
- Basic break-even and margin calculations.
None of it needs advanced mathematics. The difficulty is getting several steps right, at pace, on data you haven't seen before.
Where time gets lost
Time goes in two places: reading and calculating. You re-read an exhibit because you didn't note the axes and units the first time, and you lose more by doing full-precision arithmetic when a rough estimate would already rule out three of the four answers.
Habits that save time
- Read the question before you study the exhibit, so you know what to look for.
- Note units and periods first: thousands or millions, monthly or annual.
- Estimate before you calculate. Round the numbers, get a ballpark answer, and see which options are even possible.
- Use the answer options. If they differ by a factor of ten or by sign, you can skip most of the calculation.
- Skip and return. If a question is costing you about twice your average time, flag it and move on.
- Work out your time per question at the start. Twelve questions in 18 minutes is 90 seconds each.
Traps that cost easy points
- Percent versus percentage points. Going from 10% to 12% is +2 points, but +20%.
- Chained percentages. A 25% fall followed by a 20% rise is a 10% net fall (0.75 × 1.2 = 0.9), not a 5% fall.
- The wrong base. "20% more than" and "20% less than" start from different numbers.
- Mixed periods, such as comparing a monthly figure with an annual one.
- Tempting wrong answers. Test writers include the result of a common mistake on purpose.
A practical way to prepare
Little and often beats one long session, as in our four-week prep plan. Do a short timed set most days, review each mistake, and write down the cause: misread the unit, wrong base, arithmetic slip. Watch for the same error coming back. Drill your percentage-to-fraction conversions (12.5% is 1/8, 37.5% is 3/8, 16.7% is 1/6) until they're automatic, because they save more time than any other single habit. Then move to timed sets at the real test pace so the clock stops being a surprise. CaseClimb generates a fresh timed numerical set each time you start one, with an explanation for each answer, so you don't run out of new questions.
