Notes

METRIC (SI) UNITS
In the activity above, you practiced multiplying and dividing by powers of 10. Do you remember the trick for quickly solving these types of problems? To multiply by a power of 10, move the decimal point to the right as many places as there are zeroes in the power of 10. To divide by a power of 10, move the decimal point to the left as many places as there are zeroes in the power of 10. Here are a couple of examples.

45.25 · 1,000 = 45,250
(Move the decimal point three places to the right.)

45.25 ÷ 1,000 = 0.0425
(Move the decimal point three places to the left.)

Connections
Mass is often confused with weight because they are similar measurements. However, weight is affected by gravity and mass is not. For example, if you weighed yourself on earth and then on the moon, the two weights would be different because of gravity. Your mass, though, would be the same on earth or on the moon.
Why are you practicing multiplying and dividing by powers of 10? This is the only skill you need in order to work with the metric system! The metric system of measurement, also called the International System of Units (SI), is based on the number 10. So converting between units in the metric system is simply a matter of moving the decimal point! So take a look at the units of the metric system.

There are three basic SI units: the meter (m), liter (l), and gram (g). The meter is used to measure length, such as the distance around a track. The liter is used to measure volume, such as the amount of liquid in a soda pop bottle. The gram is used to measure mass, such as the quantity of matter inside your body. Each of these three units represents a value of 1. All the other units relate to one of these three basic units by a power of 10. A prefix is used with the base unit to show how it relates to the base unit. Take a look at the following table for the abbreviation and value of each unit.

Make note!
You may want to make a copy of this table in your notebook. You'll be using this table to help you convert between SI units. Also, you can use the sentence "King Henry Doesn't Usually Drink Chocolate Milk" to help you remember the order of the prefixes. The first letter of each word in the sentence represents a prefix from the largest unit to the smallest unit.

Prefix Abbreviation Value
kilo- k- 1,000
hecto- h- 100
deka- da- 10
base unit — 1
deci- d- 0.1
centi- c- 0.01
milli- m- 0.001
So a milligram (mg) is equivalent to 0.001 gram. A hectometer (hm) is equivalent to 100 meters. A kiloliter (kl) is equivalent to 1,000 liters.

Example:
What unit of measure is equivalent to 10 grams? What is its abbreviation?

Solution:
a dekagram, dag

Example:
What unit of measure is equivalent to 0.01 liters? What is its abbreviation?

Solution:
a centiliter, cl

Example:
What unit of measure is equivalent to 0.1 meters? What is its abbreviation?

Solution:
a decimeter, dm

Think about it!
Why do you multiply when moving from a larger unit to a smaller unit? Because it takes more of a smaller unit to represent a measurement than it takes of a larger unit. For example, to measure the length of a piece of wood in feet or inches, it takes more inches (the smaller unit) than feet (the larger unit).