Metric system:
kilometre, metre, centimetre, millimetre, tonne, kilogram, gram, milligram, litre, millilitre
excersise 4.1:
write an estimate for each of the following using a sensible unit
the length of your foot
the capacity of a car petrol tank
the mass of a cow
the quantity of water in a human body
the distance to the sun
the mass of a ship