REASONS FOR THE REASONS FOR THE METRIC SYSTEMMETRIC SYSTEM

a.k.a.a.k.a.

INTERNATIONAL SYSTEM OF UNITS INTERNATIONAL SYSTEM OF UNITS or SI Systemor SI System

(Le Systeme International d(Le Systeme International d’’Unites)Unites)

1. Used world wide• 95% of the world’s population already

uses it

2. Based on multiples of 10

• Easy to remember conversions

• Easy to calculate conversions between units (just move the decimal)

3. Based on unchanging standards

• What is the length of the original foot, inch and yard?

• How was the length of the meter determined? 1/4 of the Earth’s

circumference divided by 10,000,000

= 1 meter

What’s the circumference of the Earth in meters?

4. Interrelated Units• Units of length use to determine units of

volume (volume = l x w x h)• 1cm x 1cm x 1cm = 1cm3

– 1cm3 = 1mL (1 inch3 = 0.55 ounces)?

• Units of volume use to determine units of mass– 1mL of pure water = 1 g (1 fluid oz. = 1.04 oz.)– 1 L of pure water = 1 kg (1 gallon = 8.57 lb)

Medieval English 'doubling' method for measuring volumes

Two mouthfuls* are a jigger; two jiggers are a jack;

two jacks are a gill**; two gills are a cup;

two cups are a pint; two pints are a quart;

two quarts are a pottle; two pottles are a gallon;

two gallons are a pail; two pails are a peck;

two pecks are a bushel; two bushels are a strike;

two strikes are a coomb; two coombs are a cask;

two casks are a barrel; two barrels are a hogshead;

two hogsheads are a pipe; two pipes are a tun;

and there, my friend, my story is done!

* It's probably best to avoid cooks who use mouthfuls as measures! ** a gill was often pronounced jill.