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Here are a few recommended readings before getting started with this lesson.
Two polygons are said to be similar if their corresponding sides are proportional and their corresponding angles are congruent. Because of this, there is a relation between the perimeters of similar polygons.
If two polygons are similar, then the ratio of their perimeters is equal to the ratio of their corresponding side lengths.
Let and be the perimeters of and respectively. Let be the scale factor between corresponding side lengths. Then, based on the above diagram, the following relation holds true.
Tadeo likes playing basketball. He decides to make a miniature model of a basketball court with a length of centimeters.
A standard basketball court has a length of meters and a width of meters.
Like with perimeters, there is a relation between the areas of similar polygons.
If two figures are similar, then the ratio of their areas is equal to the square of the ratio of their corresponding side lengths.
Let and be similar figures, and and be their respective areas. The length scale factor between corresponding side lengths is Here, the following conditional statement holds true.
The statement will be proven for similar rectangles, but this proof can be adapted for other similar figures.
The area of a rectangle is the product of its length and its width.
| Area of | Area of |
|---|---|
Remove parentheses
Commutative Property of Multiplication
Associative Property of Multiplication
Now Tadeo wants to build a miniature spectator stand for his miniature basketball stadium. He plans to use the following stand as a model.
When viewed from the side, the stand looks like a right triangle. Tadeo knows that its hypotenuse is meters long and its height is meters.
Substitute values
Consider two similar polygons. Use the given information to find the scale factor, perimeter, or area of either of the polygons. Keep in mind that the given length scale factor corresponds to the ratio of Polygon to Polygon Round the answer to two decimal places if necessary.
If two figures are similar, then the ratio of their surface areas is equal to the square of the ratio of their corresponding side lengths.
Let Solid and Solid be similar solids and and be their respective surface areas. The length scale factor between corresponding linear measures is Given these characteristics, the following conditional statement holds true.
The statement will be proven for similar rectangular prisms, but this proof can be adapted to prove other similar solids as well. As shown in the diagram, let and be the dimensions of Solid and and be the dimensions of Solid
The surface area of a rectangular prism is the sum of the lateral area and the combined areas of the two identical bases. The lateral area of a rectangular prism consists of its four rectangular side areas. Notice that the areas of opposite faces are congruent.
| Surface Area of Solid | Surface Area of Solid |
|---|---|
Substitute expressions
Commutative Property of Multiplication
Remove parentheses
Factor out
What does a basketball court need if not a basketball? Tadeo turns his attention to designing a miniature basketball for his miniature stadium.
He knows that the radius of a real basketball is inches.
As with side lengths and perimeters, there is a relation between the volumes of the similar figures.
If two figures are similar, then the ratio of their volumes is equal to the cube of the ratio of their corresponding side lengths.
Let Solid and Solid be similar solids and and be their respective volumes. The length scale factor between corresponding linear measures is Given these characteristics, the following conditional statement holds true.
The statement will be proven for similar rectangular prisms, but this proof can be adapted to prove other similar solids. As shown in the diagram, let and be the dimensions of Solid and and be the dimensions of Solid
The volume of a rectangular prism is the product of its base area and its height.
| Volume of Solid | Volume of Solid |
|---|---|
Substitute expressions
Remove parentheses
Commutative Property of Multiplication
Associative Property of Multiplication
Finally, Tadeo plans to model the exterior of his miniature stadium after his favorite basketball team's stadium.
The actual stadium has a volume of cubic meters. Calculate the volume of the miniature stadium if he uses the length scale of Round the answer to two decimal places.If two figures are similar, then the ratio of their volumes is equal to the cube of the ratio of their corresponding side lengths.
Tadeo wants to complete his miniature basketball stadium with the tiny basketball players. As he places his collection of action figures of his favorite team, he thinks about the real heights and weights of the players. For one particular player, the toy figure is centimeters tall, while the real life counterpart player is about meters tall.
Tadeo supposes that the if bodies of the action figure and the real player can be modeled with two similar solids, then the weights of similar figures is related by the cube of the scale factorWhat is the length scale factor between the action figure and the human basketball player? Find the basketball player's weight using this equation. Does it make sense for a basketball player to weigh this much?