When the denominator of one fraction is a multiple of the denominator of another fraction, we can say these fractions are related fractions.

When two or more fractions share the same denominator, you can say they have a common denominator.

Use knowledge of adding and subtracting related unit fractions to solve problems

Maths

In this unit pupils will explain how to write a fraction in its simplest form when solving addition and subtraction problems and how to add and subtract related fractions. In the future unit pupils will use their fraction sense to fraction addition, subtraction and comparison explaining how to compare pairs of non-related fractions by converting to common denominators and using fraction sense.

In the prior unit pupils used representations to describe and compare two fractions. They explained the relationship within families of equivalent fractions and used their knowledge of common equivalents to compare fractions with decimals. In this unit pupils will explain how to write a fraction in its simplest form when solving addition and subtraction problems. 

Addition and subtraction of fractions

Match the fractions with common denominators.

$$ {1} \over {3}$$ + $$ {1} \over {6}$$+ $$ {1} \over {2}$$

$$ {1} \over {8}$$ + $$ {1} \over {6}$$+ $$ {1} \over {12}$$

$$ {1} \over {2}$$ + $$ {1} \over {8}$$ + $$ {1} \over {24}$$

$$ {2} \over {3}$$ + $$ {1} \over {9}$$ + $$ {1} \over {18}$$

Tick the equations where all three fractions are related fractions.

$$ {1} \over {4}$$ + $$ {1} \over {6}$$ + $$ {1} \over {2}$$

$$ {1} \over {5}$$ + $$ {1} \over {6}$$ + $$ {1} \over {35}$$

$$ {1} \over {2}$$ + $$ {3} \over {5}$$ + $$ {1} \over {24}$$

Tick the sum for the following equation: $$ {1} \over {2}$$ + $$ {1} \over {8}$$ + $$ {1} \over {16}$$ =

Tick the sum for the following equation: $$ {1} \over {2}$$ − $$ {1} \over {8}$$ − $$ {1} \over {16}$$ =

Compare the expressions using < > or =     $$ {1} \over {5}$$  − $$ {1} \over {10}$$ − $$ {2} \over {20}$$  {{ }}  $$ {2} \over {5}$$ − $$ {2} \over {10}$$ − $$ {4} \over {20}$$

one has a denominator that is a multiple of the other fraction’s denominator.

they have the same number for the numerator.

they have the same number for the denominator.

they have the same numerator and denominator.

Fractions have a common denominator when:

Type in the number to show how the numerator and denominator has been multiplied to create a related fraction.

$$ {2} \over {10}$$ − $$ {1} \over {10}$$ = ____

$$ {3} \over {15}$$ − $$ {1} \over {10}$$= ____

$$ {4} \over {20}$$ − $$ {1} \over {10}$$ = ____

$$ {5} \over {25}$$ − $$ {1} \over {10}$$ = ____

This image shows $$ {1} \over {5}$$ − $$ {1} \over {10}$$ = ____ Tick the equation which shows the appropriate related fraction.

$$ {1} \over {15}$$ − $$ {1} \over {15}$$ = ___

$$ {2} \over {15}$$ − $$ {1} \over {15}$$ = ___

$$ {3} \over {15}$$ − $$ {1} \over {15}$$ = ___

$$ {5} \over {15}$$ − $$ {1} \over {15}$$ = ___

Tick the correct equation once it has been adjusted to include the most appropriate related fraction. $$ {1} \over {3}$$ − $$ {1} \over {15}$$ = ___

Tick the correct solution: $$ {1} \over {9}$$ − $$ {1} \over {18}$$ = ___

Tick the correct solution: $$ {2} \over {3}$$ − $$ {2} \over {15}$$= ___

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