ACT Math : How to find the area of a right triangle

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #1 :Triangles

The ratio for the side lengths of a right triangle is 3:4:5. If the perimeter is 48, what is the area of the triangle?

Possible Answers:

48

108

50

240

96

Correct answer:

96

Explanation:

We can model the side lengths of the triangle as 3x, 4x, and 5x. We know that perimeter is 3x+4x+5x=48, which implies that x=4. This tells us that the legs of the right triangle are 3x=12 and 4x=16, therefore the area is A=1/2 bh=(1/2)(12)(16)=96.

Example Question #91 :Right Triangles

The length of one leg of an equilateral triangle is 6. What is the area of the triangle?

Possible Answers:

Correct answer:

Explanation:

The base is equal to 6.

The height of an quilateral triangle is equal to, whereis the length of the base.

Example Question #68 :Act Math

Find the area of the following right triangle to the nearest integerFinding_area_of_right_triangle

Note: The triangle is not necessarily to scale

Possible Answers:

None of the other answers

Correct answer:

Explanation:

The equation used to find the area of a right triangle is:where A is the area, b is the base, and h is the height of the triangle. In this question, we are given the height, so we need to figure out the base in order to find the area. Since we know both the height and hypotenuse of the triangle, the quickest way to finding the base is using the pythagorean theorem,.a = the height, b = the base, and c = the hypotenuse.

Using the given information, we can write.Solving for b, we getor.现在我们有基础和高度,我们can solve the original equation for the area of the triangle.

Example Question #69 :Act Math

Right triangle

In the above triangle, ifandwhat is the area of the triangle?

Possible Answers:

Correct answer:

Explanation:

To find the area of a triangle use the formula:

, since the base isand the height is, plugging in yields:

Example Question #71 :Act Math

A right triangle has integer sides with a ratio of, measured in.What is the smallest possible area of this triangle?

Possible Answers:

Correct answer:

Explanation:

The easiest way to find the smallest possible integer sides is to simply factor the ratio we are given. In this case,is already prime (sinceis a prime number), so the smallest possible sides which hold to this triangle areand.You may also recognize this number as a common Pythagorean triple.

The area of a triangle is expressed as, whereis the length andis the height. Since our triangle is right, we know that two lines intersect at a角,从而为我们的长度和高度.We also know that the longest side is always the hypotenuse, so the other two sides must beand

Applying our formula, we get:

Thus, the smallest possible area for our triangle is

Example Question #1 :How To Find The Area Of A Right Triangle

Right trianglehas hypotenusecm and.Find the area of the triangle, in cm2, by using

Round angles to four significant figures. Round side lengths to the nearest integer.

Possible Answers:

Correct answer:

Explanation:

To find the area of a right triangle, find the lengths of the two perpendicular legs (since this gives us our length and height for the area formula).

In this case, we know that one angle is, and SOHCAHTOA tells us that, so:

Substitute the angle measure and hypotenuse into the formula.

Isolate the variable.

Solve the left side (rounding to the nearest integer) using our Pythagorean formula:

--->Substitute known values.

--->Simplify.

广场root both sides.

So with our two legs solved for, we now only need to apply the area formula for triangles to get our answer:

So, the area of our triangle is

Example Question #1 :How To Find The Area Of A Right Triangle

Find the area of a right triangle whose height is 4 and base is 5.

Possible Answers:

Correct answer:

Explanation:

要解决,只需使用的面积的公式triangle given height h and base B.

Substitute

andinto the area formula.

Thus,

Example Question #2 :Triangles

A right triangle has a total perimeter of 12, and the length of its hypotenuse is 5. What is the area of this triangle?

Possible Answers:

10

12

6

15

3

Correct answer:

6

Explanation:

The area of a triangle is denoted by the equation 1/2 b x h.

b stands for the length of the base, and h stands for the height.

Here we are told that the perimeter (total length of all three sides) is 12, and the hypotenuse (the side that is neither the height nor the base) is 5 units long.

So, 12-5 = 7 for the total perimeter of the base and height.

7 does not divide cleanly by two, but it does break down into 3 and 4,

and 1/2 (3x4) yields 6.

另一个way to solve this would be if you recall your rules for right triangles, one of the very basic ones is the 3,4,5 triangle, which is exactly what we have here

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