Here is a 500 g bag of flour beside a 2 kg bag. How many of the small bags would you need to make one big bag?

The word 'kilo' means a thousand, so 1 kg is 1,000 g. That is why changing grams into kilograms is always a ÷ 1,000 jump, and changing kilograms into grams is always a × 1,000 jump.

Watch four conversions on the ladder. Each digit crosses three place-value columns. Crossing one column is × 10, so crossing three columns in a row is × 10 × 10 × 10, which is × 1,000. The decimal point stays anchored in one place while the digits slide past it. Look for how many columns the digits move each time.

For the last one, say what you'd do to change grams into kilograms.

Now we work through four conversions together. First 2,000 g into kilograms. Then 0.5 kg into grams. Then 1,500 ml into litres. Last, 0.6 litres into millilitres. Before we check each one, say which way the digits will shift and how many columns they cross.

Now we work through four conversions in order, each one a step harder. First 4,200 g into kilograms. Then 0.6 litres into millilitres. Then 3,750 ml into litres. The last one has two parts: a recipe needs 250 g of sugar four times, so first work out the total in grams, then convert that total into kilograms.