Choosing Appropriate Units of Measure

In the physical world around us, we come across the quantities such as time, distance, mass, area, volume, and so on. In a mathematics course, we are more interested in the units of measurements, which are used to describe the magnitude of each of these quantities.

Some units of measurement are given below:

Time

Distance (Metric) Distance (Customary) Mass (Metric)

Weight (Customary)

Second

Millimeter

Inch

Milligram

Ounce

Minute

Centimeter

Foot

Gram

Pound

Hour

Meter

Yard

Kilogram

Ton

Day

Kilometer

Mile

Metric Ton

 

Month

       

Year

       
Century        

While describing various physical quantities, it is best to use appropriate units of measure. Using other units of measure to describe a quantity gives either very small or very large number value. It becomes difficult to estimate the magnitude of the quantity, if inappropriate units are used.

Example 1:

Quantity

Appropriate unit of measure

Distance between two cities

Miles or kilometers

Height of a person

Feet and inches, or centimeters

Weight of a person

Pounds or kilograms

Height of a high-rise building

Meters or feet

Height of a mountain peak

Meters or feet

Depth of a ocean

Meters or feet

Area of a football field

Feet2 or meters2

Capacity of milk bottle

Liters

Size of a Paper

Inches or centimeters

Time taken to complete 100 meter race

Seconds

Time taken to travel between two cities by car

Hours

 

Example 2:

What is the appropriate unit of measure used to describe the width of a computer monitor?

Answer:

Imagine yourself measuring the width of a computer monitor with a tape. What is the approximate value you could get?

The width of computer monitor is usually between 10 inches and 20 inches.

We know that 1 inch = 2.54 centimeters. So, when these values are converted to centimeters, it is about 25 and 50.

Can you measure the width of the same computer in feet or meters?

Very small numbers (less than 1) are needed to express the width of the computer in feet or meters. So, it is not possible to accurately measure the width of computer monitor in feet or meters.

Therefore, the appropriate unit of measure to describe the width of a computer monitor is inches or centimeters .