Why no calculator
Bain wants to see how quickly you can extract insight from messy data — a skill consultants use daily on client engagements. A calculator removes the need to estimate, round, and triangulate, which are exactly the habits Bain is testing for.
The webcam proctor flags suspicious behavior including looking off-screen, phone use, and additional devices. Attempting to use a calculator is grounds for disqualification.
Mental math drills that actually help
Three drills cover roughly 80% of TestGorilla Numerical Reasoning questions. Each takes 10 minutes a day and improves measurably within a week.
- Percentage change in under 15 seconds: practice (new − old) ÷ old by rounding both numbers to two significant figures first.
- Ratios from messy data: practice converting any two numbers from a chart into a clean ratio (e.g., 8.2 : 12.7 ≈ 2 : 3).
- Reasonableness checks: for every answer, ask 'is this in the right order of magnitude?' before committing. Most wrong answers in timed conditions are off by a factor of 10.
Put it into practice
The fastest way to internalize the format is timed practice that mirrors the real test.
Practice numerical reasoning