Well, the metric system has been with us for a long time but there are still many children who use Imperial units when talking, often not knowing very much about them. Schools teach the metric system: society seems to want to keep the old fashioned system and it is our children who suffer.
Metric is far easier and this worksheet reminds children of the main units:
1 km = 1000 m
1 m = 100 cm
1 cm = 10 mm
1 kg = 1000 g
1 litre = 1000 ml
It is also worth reminding ourselves that a litre of water has a mass (weighs) one kilo and fits exactly into a 10 cm cube!
Rant over – try the worksheet.