Introduction to Percentages (Edexcel IGCSE Maths)

Spec point — 1.6A

Introduction to percentages

What is a percentage?

• “Per-cent” simply means “out of 100” (or “ ÷ 100”)

• Rewriting fractions as percentages means they can be compared more easily

• You can do this by finding an equivalent fraction with a denominator of 100

  • $1 \frac{1}{2} = \frac{50}{100} = 50 \%$
  • $\frac{2}{5} = \frac{40}{100} = 40 \%$
  • $\frac{3}{4} = \frac{75}{100} = 75 \%$
  • The three percentages are much easier to compare than the three fractions

• Percentages are also equivalent to decimals

  • $\begin{gathered} 100 \% & = 1 \\ 10 \% & = 0.1 \\ 1 \% & = 0.01 \\ 0.1 \% & = 0.001 \end{gathered}$
  • $\begin{gathered} 25 \% & = 0.25 \\ 2.5 \% & = 0.025 \\ 0.25 \% & = 0.0025 \end{gathered}$

• Notice that a decimal can be converted to a percentage by multiplying by 100

  • Therefore a percentage can be converted to a decimal by dividing by 100

• A fraction can be written as a percentage by finding the decimal equivalent

  • You could use your calculator to do this
  • e.g. $\frac{234}{650} = 234 \div 650 = 0.36 = 36 \%$