10.04 Story problems with perimeter
Are you ready?
Remembering how to find perimeter will help you solve problems in this lesson. Let's try this problem to practice.
Find the perimeter of the shape given.
Learn
Can you find the missing side lengths of a rectangle if you know the perimeter and two of the side lengths? Knowing how to find the perimeter of polygons can help us answer these types of questions.
Here is an example of how to find missing side lengths of a rectangle given the perimeter and two side lengths.
| Total perimeter | $=$= | all sides added together |
| $20$20 inches | $=$= | ? + ? + $6$6 inches + $6$6 inches |
| $20$20 inches | $=$= | ? + ? + $12$12 inches |
This tells us that ? + ? makes up the last $8$8 inches. These two sides will be equal, since they are opposite sides of a rectangle. This means that ? will be equal to half of $8$8 inches, which gives us our final solution.
| ? + ? | $=$= | $8$8 inches |
| ? | $=$= | $4$4 inches |
Apply
Question
A present is contained in a cube shaped box. Ribbon is wrapped around the present as shown.
If the side length of the box is $17$17 cm, what is the shortest length of the ribbon needed to neatly go around the box without overlap?
What is the total length of ribbon needed if we wrap the present in two ways, as shown below?
To find the perimeter of any polygon we add together all side lengths.