**Directional Measurements**

Because people are always curious about location, it is important to double check these details. Numbers requiring little effort to figure out can make a huge difference for readers.

To determine time, date and distance equations, the formula is distance = rate x time.

Speed and velocity are two different measurements. Speed is how fast something is moving, while velocity also indicates direction.

Something’s speed is often better represented by an average as opposed to at a particular moment in time. To determine average speed, the formula is average speed = distance / time.

Acceleration = (ending speed – starting speed) / time.

Weight and mass, like velocity and speed, are often used interchangable, but they are very different things. Mass is a measure of amount. Weight is the measure of gravity pulling on an object.

Momentum is the necessary force required to stop an object from moving. The formula is momentum = mass x velocity.

**Area Measurements**

Sometimes numbers aren’t a good way to explain how large something is. Instead, it is good to use comparisons so readers can visualize.

But sometimes not all readers will know what youre comparing, or exact mesasurements are better respresentations.

To determine the perimeter of something, use the formula perimeter = (2 x length) + (2x width).

The area of a square or rectangle can be determined by multiplying the length by the width.

Use square inches or feet to represent small spaces, or square feet, square yards or square rods to represent larger areas. Fields, farms and yards are represented by acres, and cities, states and counties are represented by square miles.

The radius of a circle is the distance from any edge to the middle. You need this to determine the circumference, which equals 2 π x radius. π, or pi, can be rounded to 3.14.

**Volume Measurements**

Liquid measurements apply to liquids in recipes, bodies of water, or other fluids.

For a rectangular solid use the formula volume = length x width x height.

Cord is a measurement that firewood is sold by. It is defined as 128 cubic feet when the wood is stacked in a line or row. It is about 8 feet long, 4 feet wide, and 4 feet high.

There are three different types of tons. A short ton is equal to 2,000 pounds. A long ton, also known as a British ton, is equal to 2,240 pounds. A metric ton is equal to 1,000 kilograms.

**The Metric System**

Americans don’t really have a good understanding of the metric system, but it is the measurement system used by the rest of the world. It is based on multiples of 10. Familiarity and acceptance are growing.

The meter is the basic unit for length. Mass is derived from this. The metric unit of foce is the Newton.

Each unit is 10 time larger than then next smaller unit in the metric system. Prefixes are added to make a larger or smaller factor. You can also just move the decimal point one unit left to for a bigger unit, or one unit right for a smaller unit.

There are some style moves associated with units.

Lowercase all units except Celcius. Lowercase symbols except for Liter or units derived from the name of a person or country. Capitalize symbols of prefixes that mean a million or more or lowercase those less than a million.

Only make names of units plural when the numerical value is more than one. Symbols are never pluralized.

Put a space between the number and the symbol. There is no need to hyphenate if it is used as a modifier before a noun.

In names or symbols for units having prefixes, there is no space between letters making up the symbol or name.

Do not use a period with metric unit names and symbols except at the end of the sentence.

A dot or period is used as the decimal point within numbers. Always write a zero before the decimal point in numbers less than zero.

**Practice**

1. If Emily is driving on I-40 east for 5 hours, at an average speed of 72 mph, how far did she drive?

2. If Food Lion wants to put a sidewalk around their entire parking lot, and the parking lot is 100 yards wide and 40 yards long, how big do they need to make the sidewalk to make it cover the entire perimeter?

3. If the radius of a circle is 14 inches, how big is the circumference of it?

4. If something is 1254 mm, how many meters is it?