Here is a quick one to puzzle over. Aoife eats 1/4 of a pizza and Conor eats 1/3 of the same pizza. Someone says they ate 2/7 of it together. Is that right?

The fraction strips show three calculations. Watch how each fraction is renamed so the parts are the same size before we add or subtract. Notice what size both strips have to become each time.

Today we work through three problems together on the board, one at a time: first 2/5 + 3/10, then 1/2 + 1/4, then 7/8 minus 3/4. For each one we clear the strips, lay both fractions on them as they start, rename them to the same size, then combine and check before moving to the next.

Today's challenge: for each pair, one pupil works at the board while the rest of the class watches and agrees the renaming aloud first. The pupil shades the answer in the common-denominator strips, then the class confirms before they press Check, which checks the final shaded answer.

Today's big idea

Coming up

Next we add and subtract mixed numbers — whole numbers and fractions together, like 2½ + 1¾ — and meet the trick of renaming across a whole.