Have you ever wondered which measurement tool you should use to measure something?
Kris went to the hardware store to purchase a new window. She has a large rectangular picture window in her house. It is almost the length of one wall of her living room. Before going to the hardware store, Kris measured the window.
Which measurement tool do you think she used? Which unit would make the most sense to measure with?
This Concept is about measurement tools and units for squares and rectangles. By the end of the Concept, you will understand how to answer these questions.
Guidance
Measurement is the system of comparing an object to a standard.
1 pound, 1 yard, and 1 liter are just a few of the standards we use. Measuring the weight of a bunch of bananas against 1 pound, the length of a football field against 1 yard, or the amount of milk needed to make a cake against 1 liter helps us understand the quantities we encounter in all aspects of our lives.
We can measure the length, the weight or the capacity of different items.
When we measure, we can use two different measurement systems.
- Customary System – the Customary System is one that you are very familiar with. We use it all the time here is the United States. The customary system uses units such as inch, foot, yard, pint, ounce, quart, pound and ton.
- Metric System – the Metric System is a system used outside of the United States. Here in the US, we use often use metrics in Science. Common units in the Metric System are millimeter, liter, gram and kilogram.
In this Concept, we will look at measuring length.
Customary units of length are inch, foot, yard and mile.
Metric units of length are millimeter, centimeter, meter and kilometer.
Measuring length always involves tools. There are a variety of tools to choose from when measuring length.
The goal in choosing a measurement tool and unit is to find the standard that most closely matches the thing you are measuring. For example, you wouldn’t want to measure the length of a city block in inches because the number would be too large and difficult to manage.
This table can give you an idea of how the different units of measurement relate to each other. Clearly an inch is smaller than a foot, just like a centimeter is smaller than a kilometer. Using this table will help you to choose appropriate units when measuring.
Customary Units of Length
\begin{align*}& \text{inch} \ (in)\\ & \text{foot} \ (ft) && 12 \ inches\\ & \text{yard} \ (yd) && 3 \ feet\\ & \text{mile} \ (mi) && 5,280 \ feet\end{align*}
Metric Units of Length
\begin{align*}& \text{millimeter} \ (mm) && \frac{1}{10} \ centimeter\\ & \text{centimeter} \ (cm) && \frac{1}{100} \ meter\\ & \text{meter} \ (m)\\ & \text{kilometer} \ (km) && 1,000 \ meters\end{align*}
Here are some items and the best units to use in measuring the length or width of them.
a) Width of a sandbox - it would be best measured in feet, yards or meters.
b) Length of a book - it would be best measured in inches or centimeters.
c) Width of a swimming pool - it would be best measured in feet, yards or meters.
d) The length of a city street - it would be best measured in miles or kilometers.
Once you have determined the appropriate unit of measurement, you have to move on to selecting an appropriate tool.
When measuring a small item, it is best to use a ruler whether it is in metrics or customary units. Rulers are used to measure inches, centimeters or millimeters.
What about squares or rectangles?
When we measure squares or rectangles, we will have to choose appropriate units of measure and appropriate tools. What do we do if a square is small?
Using a ruler would make the best sense! Then we could measure it in inches or centimeters.
If we had a large square or rectangle, such as a pool, measuring the length and width would be quite different.
Looking at the entire pool, we can see that it is in the shape of a rectangle.
Name the appropriate unit to use in each measurement situation.
Example A
The distance of a road race
Solution: Miles or Kilometers
Example B
The length of a magazine
Solution: Inches or centimeters
Example C
The width of a football field
Solution: Yards or meters
Here is the original problem once again.
Kris went to the hardware store to purchase a new window. She has a large rectangular picture window in her house. It is almost the length of one wall of her living room. Before going to the hardware store, Kris measured the window.
Which measurement tool do you think she used? Which unit would make the most sense to measure with?
Given that the window is almost the length of one of the living room walls, it would make the most sense for Kris to use a tape measure for measuring it.
Tape measures use feet.
Kris should use a tape measure and write down the measurements of the window in feet.
Vocabulary
- Measurement
- the system of comparing an object to a standard.
- Customary System
- the system of measurements that uses inches, feet and miles to name a few.
- Metric System
- the system of measurement that uses centimeters, meters and kilometers to name a few.
- Perimeter
- the distance around the edge of a figure.
- Area
- the measurement inside a figure.
Guided Practice
Here is one for you to try on your own.
Which measurement unit would be best for measuring the perimeter of this pool?
Answer
Because it is larger than a notebook, but not as large as a football field, it is best to measure the perimeter of the pool in yards or meters.
Video Review
- This is a Khan Academy video on customary and metric units of measurement
Practice
Directions:Write down which customary and metric unit would be best to measure each item.
1. The height of a sunflower
2. The depth to plant a seed in the soil
3. The height of a tree
4. The area of a garden plot
5. The distance from a garden to the local farm store
6. The length of a carrot
7. A stretch of fencing
8. The binding on a dictionary
9. The distance between two seedlings planted in the ground
10. The height of a corn stalk
11. Your shoe size
12. A piece of pipe for a water line
13. The depth of a pond or lake
14. The distance across a lake
15. The distance from your home to school
16. A bike trail from one end of a city to another end of the same city.