Here is a small problem to turn over in your head. A jug holds 2 litres, and you are filling it from a bottle that holds 500 millilitres. Before we work anything out: what is the question really asking us to find, and what unit should our answer be in?

Look at the three measure problems on the board: ribbons, apples and cups of juice. For each one, find the signal word and decide whether to add or subtract. Watch for the units, and predict the answer before we work it out together.

Now we work through some measures problems together, one at a time. We start with a length problem: a 1 m ribbon with 25 cm cut off. Then a weight problem: a 1 kg bag of flour with 250 g used. Then a capacity problem: a 1 l 500 ml jug with 600 ml poured out. For each one, before we touch the numbers, we decide: what is the signal word, do we add or subtract, and do the units match yet or must we rename first?

Now we work through these problems together, each a step harder than the last: two pieces of string joined (40 cm and 35 cm), a 1 m ribbon with a piece cut off, a 1 kg bag of apples with some eaten, and a 1 l 500 ml jug poured out. Watch for where the units do not match yet, because that is where you must rename before you calculate.