Mental Math Techniques for Aptitude Tests
Mental math techniques help you calculate faster in numerical reasoning tests. Even when calculators are allowed, quick estimation and shortcuts save time and reduce errors. Here's how to build speed.
Why Mental Math Matters in Aptitude Tests
Tests are timed. Spending 30 seconds on a calculation you could do in 10 costs you questions. Mental math also helps you spot wrong answers and estimate before using a calculator.
Key Techniques
Percentages: 10% = divide by 10. 5% = half of 10%. 20% = double 10%. To find 15% of 80: 10% = 8, 5% = 4, so 15% = 12.
Multiplication shortcuts: 25 × 4 = 100. 12 × 5 = 60. For 48 × 25: 48 ÷ 4 = 12, so 48 × 25 = 1200.
Rounding: Round to nearby numbers, calculate, then adjust. 47 × 23 ≈ 50 × 20 = 1000 (slightly low).
Division: 1/4 = 0.25, 1/5 = 0.2, 1/8 = 0.125. Know these by heart.
Practice Tips
- Do 5–10 minutes of mental math daily.
- Focus on percentages and multiplication tables up to 12.
- Practice under timed conditions.
Use numerical reasoning practice and the numerical reasoning test to apply these techniques.
Frequently Asked Questions
Should I use mental math or a calculator in the test?
Use both. Mental math for quick checks and estimation; calculator for precise multi-step calculations.
How long does it take to improve mental math?
A few weeks of daily practice can noticeably improve speed. Focus on the operations that appear most in your target test.
What if calculators are not allowed?
Mental math becomes essential. Prioritise percentage shortcuts, multiplication tables, and estimation.