Which metric unit do you use to measure the amount of gas that a car's gas tank holds? Which metric unit would you use to measure the distance to the next town? Explain why you would use these units and not smaller units.

Capacity of the gas tank . . . Liters

Distance to the next town . . . Kilometers

Smaller units would produce bigger numbers.

It's best to use the units that produce the handiest, most convenient numbers.  That way, it's easier to remember the number, write it down without mistakes, and tell other people about it.