🔢 Calculator Hacks

Non-Calculator Paper Strategies

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Paper 1 (Non-Calculator) tests your mental arithmetic, number sense, and mathematical reasoning. Here's how to excel.

Mental Arithmetic Essentials

Times Tables to 12×12

These must be instant. If you're not 100% confident:

  • Apps like Times Tables Rock Stars
  • Practice for 5 minutes daily
  • Focus on the tricky ones: 7s, 8s, 9s

Powers and Roots to Know:

Powers of 2 Powers of 3 Powers of 5 Square roots
$2^1 = 2$ $3^1 = 3$ $5^1 = 5$ $\sqrt{4} = 2$
$2^2 = 4$ $3^2 = 9$ $5^2 = 25$ $\sqrt{9} = 3$
$2^3 = 8$ $3^3 = 27$ $5^3 = 125$ $\sqrt{16} = 4$
$2^4 = 16$ $3^4 = 81$ $5^4 = 625$ $\sqrt{25} = 5$
$2^5 = 32$ $3^5 = 243$ $\sqrt{36} = 6$
$2^{10} = 1024$ $\sqrt{49} = 7$

Prime Numbers to 50: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47

Multiplication Strategies

Grid Method for 2-digit × 2-digit:

$23 \times 47$

40 7
20 800 140
3 120 21

$= 800 + 140 + 120 + 21 = 1081$

Multiplying by 5: Multiply by 10, then halve $48 \times 5 = 480 \div 2 = 240$

Multiplying by 25: Multiply by 100, then divide by 4 $36 \times 25 = 3600 \div 4 = 900$

Multiplying by 9: Multiply by 10, subtract the original $37 \times 9 = 370 - 37 = 333$

Division Strategies

Short Division (Bus Stop): Keep it neat, write remainders small, carry properly

Dividing by 5: Double and divide by 10 $135 \div 5 = 270 \div 10 = 27$

Dividing by 25: Multiply by 4 and divide by 100 $175 \div 25 = 700 \div 100 = 7$

Fraction Calculations

Adding/Subtracting:

  1. Find the LCM of denominators
  2. Convert each fraction
  3. Add/subtract numerators
  4. Simplify if needed

$\frac{2}{3} + \frac{3}{4} = \frac{8}{12} + \frac{9}{12} = \frac{17}{12} = 1\frac{5}{12}$

Multiplying: Multiply numerators, multiply denominators, simplify

$\frac{2}{3} \times \frac{4}{5} = \frac{8}{15}$

Dividing (KFC — Keep, Flip, Change): Keep the first, flip the second, change to multiplication

$\frac{2}{3} \div \frac{4}{5} = \frac{2}{3} \times \frac{5}{4} = \frac{10}{12} = \frac{5}{6}$

Percentage Calculations

Finding 10%: Divide by 10 Finding 1%: Divide by 100 Build up from these:

Find 17.5% of £240

10% = £24 5% = £12 2.5% = £6

17.5% = £24 + £12 + £6 = £42

Percentage increase/decrease: Original × multiplier

  • Increase by 20%: × 1.2
  • Decrease by 15%: × 0.85
  • Increase by 5%: × 1.05

Checking Your Work

Inverse Operations:

  • Did subtraction? Add to check
  • Did division? Multiply to check

Estimation: Before detailed calculation, estimate the rough answer

Digit Sum (for divisibility by 9): Add the digits; if sum is divisible by 9, so is the original

Layout Matters

On non-calculator papers:

  • Write clearly — examiners can't give marks for work they can't read
  • Line up place values in column addition/subtraction
  • Show all carrying/borrowing marks
  • Don't squeeze too much into small spaces