New
New
Year 6
Explain how to subtract related unit fractions
I can explain how to subtract related unit fractions
New
New
Year 6
Explain how to subtract related unit fractions
I can explain how to subtract related unit fractions
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Lesson details
Key learning points
- Fractions need to have the same denominator if you are to subtract them.
- Common multiples help you to convert a fraction to a common denominator.
- The language of unitising helps you to subtract fractions with the same denominators.
- When subtracting fractions with the same denominators you just subtract the numerators.
Keywords
Related fractions - When the denominator of one fraction is a multiple of the denominator of another fraction, we can say these fractions are related fractions.
Common denominator - When two or more fractions share the same denominator, you can say they have a common denominator.
Common misconception
Pupils try to subtract the numerators and the denominators from one another for each fraction.
Represent each fraction using a model that draws out the equivalence of the fractions and the need for the same counting unit (denominator). Revisit previous analogies regarding sharing a common counting unit such as animals for cats and dogs.
When subtracting a fractional part, present opportunities where the part is physically taken away as well as simply just being crossed out. This will help pupils to see the reductive and partitive structures of subtraction that they have been taught throughout the curriculum.
Teacher tip
Licence
This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).
Lesson video
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Starter quiz
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6 Questions
Q1.
What fraction of the shape is shaded?
Correct answer: $$ {2} \over {9}$$
$$ {2} \over {9}$$
$$ {2} \over {7}$$
$$ {1} \over {4}$$
$$ {7} \over {9}$$
Q2.
What fraction of the shape is shaded?
Correct answer: $$ {3} \over {9}$$
$$ {3} \over {9}$$
$$ {1} \over {6}$$
$$ {1} \over {9}$$
$$ {6} \over {9}$$
Q3.
Tick the fractions in their simplest form.
$$ {5} \over {15}$$
Correct answer: $$ {11} \over {14}$$
$$ {11} \over {14}$$
Correct answer: $$ {1} \over {6}$$
$$ {1} \over {6}$$
$$ {2} \over {18}$$
Q4.
What fraction of the whole shape is shaded?
$$ {4} \over {16}$$
Correct answer: $$ {4} \over {12}$$
$$ {4} \over {12}$$
$$ {1} \over {8}$$
Correct answer: $$ {1} \over {3}$$
$$ {1} \over {3}$$
Q5.
Tick the sum in its simplest form. $$ {3} \over {5}$$ + $$ {7} \over {5}$$ =
$$ {10} \over {5}$$
$$1 {5} \over {5}$$
Correct answer: 2
2
$$ {10} \over {10}$$
1
Q6.
Tick the difference in its simplest form. $$ {20} \over {4}$$ − $$ {5} \over {4}$$
$$ {15} \over {4}$$
Correct answer: $$3 {{3} \over {4}}$$
$$3 {{3} \over {4}}$$
$$ {3} \over {4}$$
$$ {3} \over {2}$$
Exit quiz
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6 Questions
Q1.
When one fraction has a denominator that is a multiple of another fraction, the fractions are called:
Correct answer: related fractions.
related fractions.
common denominators.
improper fractions.
mixed numbers.
Q2.
This image shows $$ {1} \over {4}$$ − $$ {1} \over {12}$$ = ____ Tick the equation which shows the equivalent related fraction.
$$ {2} \over {12}$$ − $$ {1} \over {12}$$ = ____
Correct answer: $$ {3} \over {12}$$ − $$ {1} \over {12}$$ = ____
$$ {3} \over {12}$$ − $$ {1} \over {12}$$ = ____
$$ {4} \over {12}$$ − $$ {1} \over {12}$$ = ____
$$ {5} \over {12}$$ − $$ {1} \over {12}$$ = ____
Q3.
This image shows $$ {1} \over {5}$$ − $$ {1} \over {10}$$ = ____ Tick the equation which shows the appropriate related fraction.
Correct answer: $$ {2} \over {10}$$ − $$ {1} \over {10}$$ = ____
$$ {2} \over {10}$$ − $$ {1} \over {10}$$ = ____
$$ {3} \over {15}$$ − $$ {1} \over {10}$$ = ____
$$ {4} \over {20}$$ − $$ {1} \over {10}$$ = ____
$$ {5} \over {25}$$ − $$ {1} \over {10}$$ = ____
Q4.
This image shows $$ {1} \over {5}$$ − $$ {1} \over {20}$$ = ____ Tick the equation which shows the appropriate related fraction.
$$ {2} \over {10}$$ − $$ {1} \over {20}$$ = ___
$$ {3} \over {15}$$ − $$ {1} \over {20}$$ = ___
Correct answer: $$ {4} \over {20}$$ − $$ {1} \over {20}$$ = ___
$$ {4} \over {20}$$ − $$ {1} \over {20}$$ = ___
$$ {5} \over {25}$$ − $$ {1} \over {20}$$ = ___
Q5.
Tick the correct equation once it has been adjusted to include the most appropriate related fraction. $$ {1} \over {4}$$ − $$ {1} \over {12}$$ = ___
$$ {1} \over {4}$$ − $$ {3} \over {4}$$ = ___
$$ {2} \over {8}$$ − $$ {1} \over {12}$$ = ___
Correct answer: $$ {3} \over {12}$$ − $$ {1} \over {12}$$ = ___
$$ {3} \over {12}$$ − $$ {1} \over {12}$$ = ___
$$ {1} \over {8}$$ − $$ {1} \over {8}$$ = ___
Q6.
Tick the correct solution: $$ {1} \over {8}$$ − $$ {1} \over {16}$$ = ___
$$ {1} \over {8}$$
$$ {1} \over {4}$$
Correct answer: $$ {1} \over {16}$$
$$ {1} \over {16}$$
$$ {2} \over {16}$$