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Percentages Toolkit

Number

Hundredths in another form

  • A percentage counts hundredths, so the per cent sign stands for division by 100
  • Any percentage therefore has a fraction form and a decimal form
    • 35% is 35/100 and 0.35
  • Converting a fraction to a percentage means scaling it to a denominator of 100, or dividing out and multiplying by 100
    • 7/20 scales to 35/100, which is 35%
    • 3/8 divides to 0.375, which is 37.5%
  • Percentages make competing fractions directly comparable, which is why questions ask for them

The multiplier

  • The multiplier is the decimal a percentage corresponds to
    • 18% has multiplier 0.18
    • 126% has multiplier 1.26
  • Multiplying by it is the fastest route to a percentage of an amount on the calculator papers