We are learning to add and subtract fractions with the same and related denominators by renaming fractions so the parts are the same size.
I will be successful when I can…
- explain why the parts must be the same size before I add or subtract
- rename a fraction using equivalent fractions
- add and subtract fractions like 1/3 + 1/6 and 7/8 - 1/4
- write answers in simplest form, using mixed numbers when the answer passes one whole
Mini whiteboards ready!
Fractions
- In 3/8, what does the 8 tell us? What does the 3 tell us?
- Show me two fractions equivalent to 1/3.
Multiples
- Is 8 a multiple of 4?
- Is 9 a multiple of 6?
- Which of 5, 10, 12 are multiples of 5?
You can only add or subtract parts that are the SAME SIZE.
2 apples + 1 apple = 3 apples. 2 fifths + 1 fifth = 3 fifths.
The denominator is just the name of the part. Adding fractions is counting — and you can't count thirds and sixths together any more than you can count apples and oranges together.
Quick check on whiteboards: 3/8 + 2/8 = ?
1/3 + 1/6 — thirds and sixths are different names. But 6 is a multiple of 3, so we only need to rename ONE fraction.
SAME? → RENAME → COUNT & SIMPLIFY
Your turn on whiteboards: 9/10 - 2/5 (don't forget simplest form!)
Chant it before each one: "Same? Count. Different? Rename!"
- 3/8 + 2/8
- 1/2 + 1/4
- 2/3 + 1/6
- 9/10 - 2/5
- 3/4 + 1/2 ← this one goes past a whole…
Ali says: 1/2 + 1/4 = 2/6
Is Ali right? Prove your answer with the fraction wall or a diagram.
- Thumbs up if you agree with Ali, thumbs down if you disagree.
- Convince your partner in 30 seconds.
Independent work — the worksheet
- Everyone: Sections 1–3
- Most: Sections 4–5 (mixed numbers & worded problems)
- Challenge: Section 6
Show the renaming step for every question in Sections 3–6. Fraction walls stay on desks — using the model is a strategy, not cheating!