Add fractions with the same denominator and generalise the rule | Maths

Starter quiz

Which of these definitions describes the sum?
- A number added to another number.
- All of the parts added together. ✓
What is the missing number in this bar model?
- '2' ✓
What addition is being shown by this number line?
- 10 = 50 + 40
- 40 + 10 = 50
- 10 + 40 = 50 ✓
- 40 = 50 + 10
Each marble in a bag is $\frac{1}{9}$ of the whole bag. How many marbles are there in the bag?
- 1
- 10
- 9 ✓
- 12
$What is the missing fraction in this bar model?$

What is the missing fraction in this bar model?
- $\frac{1}{3}$
- $\frac{1}{4}$
- $\frac{1}{5}$ ✓
- $\frac{1}{6}$
Select the correct sum. $\frac{2}{7}$ + $\frac{4}{7}$ = ___
- $\frac{6}{7}$ ✓
- $\frac{7}{6}$
- $\frac{6}{14}$
- $\frac{8}{14}$

Exit quiz

Look at the image. What is the missing label marked with a question mark?
- addend
- sum ✓
- part
Look at the number line. The missing addend is ___
- $\frac{1}{10}$
- $\frac{2}{10}$ ✓
- $\frac{3}{10}$
- $\frac{5}{10}$
What addition is being represented on this number line?
- $\frac{1}{8}$ + $\frac{4}{8}$ = $\frac{3}{8}$
- $\frac{6}{8}$ + $\frac{5}{8}$ = $\frac{1}{8}$
- $\frac{3}{8}$ + $\frac{3}{8}$ = $\frac{6}{8}$
- $\frac{1}{8}$ + $\frac{3}{8}$ = $\frac{4}{8}$ ✓
What is the sum of this equation? $\frac{3}{7}$ + $\frac{2}{7}$ + $\frac{1}{7}$ = ___
- $\frac{6}{14}$
- $\frac{8}{7}$
- $\frac{6}{7}$ ✓
What is the correct sum for this equation? ___ = $\frac{4}{20}$ + $\frac{6}{20}$ + $\frac{6}{20}$
- $\frac{16}{20}$ ✓
- $\frac{10}{20}$
- $\frac{15}{60}$
Which of the following numbers could be used to complete this inequality?
- 1 ✓
- 2 ✓
- 3
- 4

Worksheet

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Presentation

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Lesson Details

Key learning points

To add fractions with the same denominator you add the numerators using the language of unitising.
If 2 plus 3 is equal to 5 then 2 one sevenths plus 3 one sevenths is equal to 5 one sevenths.
If fractions have the same denominator they can be added.

Common misconception

In the addition of fractions, many children will try to add together both the numerator and denominator.

Show the children many completed examples using representations alongside the fraction notation. Encourage them to make generalisations and spot that the denominator remains the same because it is the unit.

Keywords

Generalisation - A generalisation is a statement or rule that applies correctly to all relevant cases.
Denominator - A denominator is the bottom number in a fraction. It shows how many parts a whole has been divided into.
Numerator - A numerator is the top number in a fraction. It shows how many parts we have.