High School Math : How to find the area of an acute / obtuse triangle

Study concepts, example questions & explanations for High School Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : How To Find The Area Of An Acute / Obtuse Triangle

Find the area of a triangle whose base is \(\displaystyle 14in\) and whose height is \(\displaystyle 2ft\).

Possible Answers:

\(\displaystyle 336in ^{2}\)

\(\displaystyle 136in^{2}\)

\(\displaystyle 196in^{2}\)

\(\displaystyle 168in^{2}\)

\(\displaystyle 186in^{2}\)

Correct answer:

\(\displaystyle 168in^{2}\)

Explanation:

This problem is solved using the geometric formula for the area of a triangle.  

\(\displaystyle A=\frac{1}{2}b*h\)

Convert feet to inches.

\(\displaystyle \dpi{100} \frac{2ft}{1}*\frac{12in}{1ft}=24in\)

\(\displaystyle A=\frac{1}{2}*14in*24in\)

\(\displaystyle A=168in^{2}\)

Example Question #111 : Triangles

If triangle ABC has vertices (0, 0), (6, 0), and (2, 3) in the xy-plane, what is the area of ABC?

Possible Answers:

9

20

18

12

10

Correct answer:

9

Explanation:

Sat-triangle

Sketching ABC in the xy-plane, as pictured here, we see that it has base 6 and height 3. Since the formula for the area of a triangle is 1/2 * base * height, the area of ABC is 1/2 * 6 * 3 = 9.

Example Question #1 : How To Find The Area Of An Acute / Obtuse Triangle

What is the area of a triangle with a height of \(\displaystyle 7\) and a base of \(\displaystyle 4\)?

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 14\)

\(\displaystyle 28\)

\(\displaystyle 24\)

Correct answer:

\(\displaystyle 14\)

Explanation:

When searching for the area of a triangle we are looking for the amount of the space enclosed by the triangle.

The equation for area of a triangle is

Plug the values for base and height into the equation yielding

 \(\displaystyle \frac{1}{2}(4)(7)=Area\)

Then multiply the numbers together to arrive at the answer \(\displaystyle 14\).

Example Question #61 : Triangles

The height, \(\displaystyle h\), of triangle \(\displaystyle PQR\) in the figure is one-fourth the length of \(\displaystyle PQ\). In terms of h, what is the area of triangle \(\displaystyle PQR\)?

Vt_p5

 

Possible Answers:

2h^{2}\(\displaystyle 2h^{2}\)

3h^{2}\(\displaystyle 3h^{2}\)

\frac{1}{2}h^{2}\(\displaystyle \frac{1}{2}h^{2}\)

h^{2}\(\displaystyle h^{2}\)

Correct answer:

2h^{2}\(\displaystyle 2h^{2}\)

Explanation:

If \dpi{100} \small h=\frac{1}{4}\(\displaystyle \dpi{100} \small h=\frac{1}{4}\) *\dpi{100} \small \overline{PQ}\(\displaystyle \dpi{100} \small \overline{PQ}\), then the length of \dpi{100} \small \overline{PQ}\(\displaystyle \dpi{100} \small \overline{PQ}\) must be \dpi{100} \small 4h\(\displaystyle \dpi{100} \small 4h\).

Using the formula for the area of a triangle (\frac{1}{2}bh\(\displaystyle \frac{1}{2}bh\)), with \dpi{100} \small b=4h\(\displaystyle \dpi{100} \small b=4h\), the area of the triangle must be 2h^{2}\(\displaystyle 2h^{2}\).

Learning Tools by Varsity Tutors