10 Useful Calculator Tricks Every Student Should Know

10 Calculator Tricks That Save Time

Trick 1: Percentage Calculations — Without Division

Most people calculate "20% of 350" by doing 350 × 0.20 = 70. But there's a faster way:

• Enter: 350 × 20 % = → answer: 70 (works on most calculators)
• For "what % is 70 of 350?": 70 ÷ 350 × 100 = 20%
• For "350 + 15%": Enter 350 + 15 % = → answer: 402.5
• For "350 − 20% discount": Enter 350 − 20 % = → answer: 280

Trick 2: Ans Key — Chain Calculations

The ANS (answer) key stores the result of your last calculation and lets you use it immediately in the next. Example: Finding compound interest step by step — calculate principal × rate → press ANS × rate → repeat for each period without retyping the long number.

Trick 3: Memory Functions (M+, M−, MR, MC)

• M+ → adds current display to memory
• M− → subtracts current display from memory
• MR → recalls memory value
• MC → clears memory

Use case: Calculating total with subtotals — calculate first item cost → M+ → calculate second → M+ → ... → MR for grand total.

Trick 4: Quick Square Root Check

To check if a number is a perfect square: enter the number → press √ → if the answer is a whole number, it's a perfect square. Example: √1764 = 42 (perfect square). √1800 = 42.426... (not perfect square).

Trick 5: Converting Fractions to Decimals Instantly

Any fraction can be converted by simply dividing: 7/8 → press 7 ÷ 8 = → 0.875. For recurring decimals like 1/3 = 0.333..., the calculator shows as many digits as its display allows. For back-conversion, recognise common ones: 0.25 = 1/4, 0.5 = 1/2, 0.75 = 3/4, 0.333 = 1/3.

Trick 6: Checking Divisibility Quickly

Divide the number by the potential factor. If the result is a whole number (no decimal), it's divisible. Example: Is 1,247 divisible by 7? → 1247 ÷ 7 = 178.14... (No). By 11? → 1247 ÷ 11 = 113.36... (No). By 13? → 1247 ÷ 13 = 95.923... (No).

Trick 7: Scientific Notation for Very Large/Small Numbers

For numbers like 3,400,000 — enter 3.4 EXP 6 (meaning 3.4 × 10⁶). For 0.000052 — enter 5.2 EXP −5. The EXP button (or EE on some calculators) prevents entry errors with many zeros.

Trick 8: Verify Answers Using Reverse Operation

Always verify multiplication by dividing: if 123 × 456 = 56,088, then 56,088 ÷ 456 should = 123. This catches calculator entry errors instantly. Same for addition (subtract result minus one addend), square roots (square the answer), etc.

Trick 9: Approximation Before Calculating

Before pressing = on any complex calculation, estimate the expected magnitude. 23.7 × 198.4 ≈ 24 × 200 = 4,800. If your calculator gives 47,012, you know a decimal point was missed or a digit entered wrong. The answer should be ~4,700, not 47,000.

Trick 10: Using π and e Precisely

Never type 3.14 for pi — always use the dedicated π button (accurate to 10+ decimal places). Same for e. Using 3.14 instead of π in area calculations introduces 0.05% error — tiny for most purposes, but significant in physics and engineering calculations.

Common Calculator Mistakes to Avoid in Exams

• Wrong angle mode: Check DEG/RAD before every trig problem
• Order of operations error: 2 + 3 × 4 ≠ (2+3) × 4. Use brackets when in doubt
• Forgotten negative sign: −3² ≠ 3². −3² = −9, (−3)² = +9
• Pressing = mid-calculation: Intermediate = press changes the calculation flow
• Battery issues: Always carry spare batteries to exams

Frequently Asked Questions