· The meter for length · The kilogram for mass · The second for time
Examples:
A kilometer is 1,000 meters A centimeter is 1/100th (one-hundredth) of a meter A cubic meter is the volume of a cube whose sides are 1 meter long A liter is 1/1,000th (one-thousandth) of a cubic meter A tonne is 1,000 kilograms