Rukasha Maths

GCSE maths Beta

Fractions and decimals · Revision guide

Foundation · Number · 1 page in the PDF

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Learning objectives

  • Add, multiply and divide fractions.
  • Convert between fractions and decimals.

Key ideas

Use equal denominators before adding or subtracting fractions.

Multiply numerators and multiply denominators.

ab×cd=acbd(b,d≠0)\frac{a}{b}\times\frac{c}{d}=\frac{ac}{bd}\quad(b,d\ne0)

To divide by a non-zero fraction, multiply by its reciprocal.

Convert to a decimal by dividing the numerator by the denominator.

Find a fraction of an amount: divide by the denominator, then multiply by the numerator.

Worked examples

Example 1

Add the fractions and simplify.

Use twelfths.

34+23=912+812=1712\frac34+\frac23=\frac9{12}+\frac8{12}=\frac{17}{12}
1712=1512\frac{17}{12}=1\frac5{12}
15121\frac5{12}

Example 2

Write the decimal as a fraction in its simplest form.

0.35=35100=7200.35=\frac{35}{100}=\frac7{20}
720\frac7{20}

Watch out

Adding denominators changes the size of the parts. Keep the common denominator and add only the numerators.