DeepMaths / Fun Maths

Fun Maths Book 2 Online Learning Programme

For Year 4 and Year 5

Chapter 4: Fractions

Fractions, Equivalence and Unlike Denominators

Make denominators match before adding or subtracting, and connect fractions to equal parts.

Fun Maths Book 2 pages 51-675 minutes

AI teacher

Press Start to hear a short classroom-style explanation. If sound is unavailable, the full script is shown below.

Voice: Browser voice

Workbook pages

Fun Maths Book 2 pages 51-67

Use equivalent fractions, add and subtract fractions, and find fractions of amounts.

AI explanation

The AI teacher uses fraction bars to show that fractions must name the same-sized parts before they can be combined. Equivalent fractions are treated as renaming the same amount, not changing its size.

  1. 1The denominator tells the size of each part.
  2. 2To add or subtract fractions, the parts must be the same size.
  3. 3Use equivalent fractions to make the denominators match.
  4. 4For a fraction of an amount, divide by the denominator first, then multiply by the numerator.

Think with the AI teacher

Today we will make fractions feel fair and visual. Fractions only combine safely when the parts are the same size.

Question 1

Pause 5s

Which is bigger: one half or one sixth? How do you know?

After thinking

One half is bigger because the whole is split into fewer, larger pieces.

Excellent. You looked at the size of the pieces.

Question 2

Pause 5s

Why can we change 1/3 into 2/6 without changing the amount?

After thinking

We cut each third into two equal pieces, so the amount stays the same but the name changes.

Beautiful reasoning. Equivalent means same value, new name.

Question 3

Pause 5s

Why is 1/4 + 1/2 not 2/6?

After thinking

The denominators name the size of the parts. We do not add the part sizes together.

Great catch. You avoided one of the biggest fraction mistakes.

Deep structure

What children discover

Children discover that the denominator controls the size of each part, so equivalent fractions rename the same amount.

Common mistake

Children often add denominators, such as 1/4 + 1/2 = 2/6.

Future connection

Fraction structure supports ratio, percentages, algebraic fractions, probability and later calculus with fractional powers.

RatioPercentagesAlgebraic fractionsProbability

Animated demonstration

See the maths move

Fraction strips resize into common denominators, then shaded pieces slide together or apart to show addition and subtraction.

Fraction strips resize into common denominators so children can see why same-size parts must come before adding or subtracting.

1/3 = 2/6

2/6

2/6 + 1/6 = 3/6

Same-size parts first

Make denominators match, then add or subtract the numerators.

1/3 + 1/6 = 1/2

Guided examples

Adding unlike denominators

Find 1/3 + 1/6.

  1. 1.The denominators are 3 and 6.
  2. 2.Change 1/3 into sixths: 1/3 = 2/6.
  3. 3.Now add sixths: 2/6 + 1/6 = 3/6.
  4. 4.Simplify 3/6.
Answer: 1/2

Fraction of an amount

Find 3/5 of 45.

  1. 1.Divide by the denominator: 45 รท 5 = 9.
  2. 2.Multiply by the numerator: 9 x 3 = 27.
Answer: 27

Interactive practice

Try it now

Draw or imagine fraction bars before adding fractions with unlike denominators.

0/3 correct

Which fraction is equivalent to 2/3?

Find 1/4 + 1/2.

Find 2/3 of 30.

Review

Say why 1/4 + 1/2 is not 2/6 before opening the fraction pages.

Explain why 2/6 and 1/3 are the same amount using equal parts.

Parent signal

If the child adds denominators, return to fraction bars and make the parts the same size.

Well done. You are learning to see fractions, not just calculate them.