Fractions of Amounts (Edexcel IGCSE Maths A): Revision Note

Fractions of amounts

What is a fraction?

• A fraction is written as  where a and b are integers

  • The number on the top, a, is called the numerator

  • The number on the bottom, b, is called the denominator

• The values of the numerator and denominator tell us about the size of the fraction 

  • The denominator is how many parts each whole number is split into

  • The numerator is how many parts you have

    • For example, means that each whole number is divided into 3 parts and you have 2 of these parts

• A fraction is less than 1 if the numerator is smaller than the denominator

• A fraction is more than 1 if the number is bigger than the denominator

How do I shade a fraction on a diagram?

• Divide by the denominator and multiply by the numerator

  • To shade  of a grid of 20 squares

    • Divide 20 squares by 5 to get 4 squares

    • Multiply this amount by 3 to get 12 squares 

    • Shade 12 squares

  • To shade of a circle

    • Divide the circle into four quarters by drawing a horizontal and a vertical line through the centre

    • Shade one of these quarters

How do I find a fraction of an amount?

• Method 1
  Divide by the denominator and multiply by the numerator

  • To find  of , divide it by 3

    • 

  • To find of , divide it by 5 then multiply it by 2

    • , then 

• Method 2
  Multiply the amount by the fraction

  • To find of , multiply them together

    •