Idiot\'s Guides Basic Math and Pre-Algebra

Measurement 347

When you’re changing units within a system, the thing to remember is balance. If you’re chang-

ing to a unit of a smaller size, you’ll have more of them. If your new unit is bigger, you’ll have

fewer. And always, it’s about 10. Multiply by 10 if you’re going to a smaller unit, and divide by 10

to get to a bigger unit.

Base

1,000

millimeters

100

centimeters

10

decimeters

1 meter 0.1

decameter

0.01

hectometer

0.001

kilometer

1,000

milligrams

100

centigrams

10 decigrams 1 gram 0.1 decagram 0.01

hectogram

0.001

kilogram

1,000

milliliters

100

centiliters

10 deciliters 1 liter 0.1 decaliter 0.01

hectoliter

0.001

kiloliter

Customary System

What’s commonly called the customary system is a system that developed over time and remains

popular in the U.S. and a few other spots around the world. It is very similar to the British impe-

rial system, as both were derived from English units. The customary system was not designed as

a unified system, so there are many different rules to remember.

Length

In the customary system, length is measured in units like inches, feet, yards, and miles.

Unit Approximation Conversion

Inch From the knuckle to the tip of your thumb

Foot The length of a large man’s foot 12 inches = 1 foot

Yard The height of the kitchen counter 3 feet = 1 yard

Mile A 20-minute walk 5,280 feet = 1,760 yards = 1 mile

Mass (Weight)

The customary system measures mass (but often calls it weight) in ounces, pounds, and, for really

heavy things, tons.

Unit Approximation Conversion

Ounce Ten pennies

Pound A package of butter or bacon, or a football 16 ounces = 1 pound

Ton A car 2,000 pounds = 1 ton