Here is a one-litre bottle, a cup and a teaspoon.

About how many cups of water do you think it takes to fill the whole bottle? More than five? More than ten?

A millilitre is a tiny amount — about one drop from a spoon. A litre is a big amount — a full bottle of water.

If you poured one whole litre out drop by drop into tiny millilitre cups, you would fill one thousand of them. So one litre and one thousand millilitres are the very same amount of water. We just measure it with the big unit or the small unit.

We use litres for big amounts, like bottles and jugs. We use millilitres for small amounts, like spoons and medicine cups.

Today we measure four containers together at the water tray, one at a time: a cup, then a mug, then a yoghurt pot, then a small flask.

For each one we estimate first — write your guess in millilitres in your copy — then we pour the water in, read the jug at eye level, and check how close we were.

Now for the practice round. Estimate then measure how much four more containers hold, biggest worth most:

an egg cup, then a mug, then a yoghurt pot, then a small lunch flask. Record each in millilitres.

Stretch: which two of your containers together would just fill the one-litre bottle?