Shortcut Techniques for Calculations
In numerical reasoning tests, every second counts. Shortcuts help you calculate faster without sacrificing accuracy. Here are the most useful techniques.
Multiplication Shortcuts
× 10, × 100, × 1000 – Move the decimal point. 47 × 10 = 470.
× 5 – × 5 = × 10 ÷ 2. 48 × 5 = 480 ÷ 2 = 240.
× 9 – × 9 = × 10 − × 1. 23 × 9 = 230 − 23 = 207.
× 11 – × 11 = × 10 + × 1. 35 × 11 = 385.
× 25 – × 25 = × 100 ÷ 4. 44 × 25 = 1100.
× 15 – × 15 = × 10 + × 5. 24 × 15 = 360.
Division Shortcuts
÷ 10, ÷ 100 – Move the decimal point left. 470 ÷ 10 = 47.
÷ 5 – ÷ 5 = × 2 ÷ 10. 240 ÷ 5 = 48.
÷ 25 – ÷ 25 = × 4 ÷ 100. 500 ÷ 25 = 20.
Percentage Shortcuts
10% of X – X ÷ 10. 10% of 480 = 48.
5% of X – Half of 10%. 5% of 480 = 24.
15% of X – 10% + 5%. 15% of 480 = 72.
20% of X – X ÷ 5. 20% of 250 = 50.
25% of X – X ÷ 4. 25% of 80 = 20.
50% of X – X ÷ 2. 50% of 340 = 170.
Squaring Shortcuts
Numbers ending in 5 – (n5)² = n×(n+1) followed by 25. 35² = 1225. 75² = 5625.
When to Use Shortcuts
- Mental math – When a calculator isn't allowed, shortcuts are essential.
- Verification – Use a shortcut to quickly check your answer.
- Estimation – Shortcuts often give good approximations.
Don't over-rely on shortcuts. If numbers are awkward, use a calculator or standard method. Practice until shortcuts become automatic.
Practice with numerical reasoning questions and the numerical reasoning test.
Frequently Asked Questions
Should I memorise all these shortcuts?
Focus on the most useful: × 10/100, × 5, × 25, ÷ 5, 10%/5%/20%/25%/50% of X. The percentage shortcuts are especially valuable.
What if the shortcut doesn't apply?
Use standard calculation. Don't force shortcuts.
How do I practise shortcuts?
Do timed drills with numbers that fit the shortcuts. Repeat until automatic.