Remember the triangles in the median of the last Concept? Take a look.
To figure this out, you will need to know how to use a formula and find the missing dimension of a triangle. This Concept will teach you how to do that.
Sometimes a problem will give us the area and ask us to find one of the dimensions of the triangle—either its base or its height. We simply put the information we know in for the appropriate variable in the formula and solve for the unknown measurement.
Remember, when you divide both sides by a fraction, you need to multiply by its reciprocal. To divide by one-half then, we multiply by 2. Keep this in mind when you use the area formula.
Now try a few of these on your own.
Given the area and one other dimension, find the missing dimension of each triangle.
Base = 4 inches, Area = 6 sq. inches, what is the height?
Base = 5 feet, Area = 7.5 sq. feet, what is the height?
Base = 7 meters, Area = 17.5 sq. meters, what is the height?
Here is the original problem once again.
To figure this out, we can use the formula for finding the area of a triangle.
Now substitute in the given values.
This is our answer.
Here are the vocabulary words in this Concept.
a figure with three sides and three angles.
the space enclosed inside a two-dimensional figure.
the bottom part of the triangle
the length of the triangle from the base to the vertex
Here is one for you to try on your own.
Find the missing base of the triangle.
To figure this out, we can solve for the base by using the formula for area of a triangle.
Now we fill in the given information.
Here is a video for review.
- This is a James Sousa video on finding the area of a triangle.
Directions: Find the missing base or height given the area and one other dimension.
1. Area = 13.5 sq. meters, Base = 9 meters
2. Area = 21 sq. meters, Base = 7 meters
3. Area = 12 sq. meters, Base = 8 meters
4. Area = 33 sq. ft, Base = 11 feet
5. Area = 37.5 sq. ft. Base = 15 feet
6. Area = 60 sq. ft., height = 10 ft.
7. Area = 20.25 sq. in, height = 4.5 in
8. Area = 72 sq. in, height = 8 in
9. Area = 22.5 sq. feet, height = 5 feet
10. Area = 12 sq. in, height = 4 in
11. Area = 45 sq. in, height = 9 in
12. Area = 84 sq. ft, height = 12 ft
13. Area = 144 sq. in, height = 16 in
14. Area = 144.5 sq. ft, height = 17 ft.
15. Area = 123.5 sq. in, height = 19 in