Area of a Triangle Practice Problems and Solutions

Master triangle area calculations with step-by-step practice problems. Learn formulas for right triangles, solve real-world examples, and build confidence.

📚Master Triangle Area Calculations with Interactive Practice
  • Calculate area of right triangles using the legs formula
  • Apply the base × height ÷ 2 formula for all triangle types
  • Solve complex problems involving perimeter and area relationships
  • Find missing measurements when area is given
  • Work with percentage-based triangle problems step-by-step
  • Identify and correct errors in triangle area calculations

Understanding Area of a right triangle

Complete explanation with examples

Formula to find the area of a right triangle

The area of a right triangle is an important subtopic that is repeated over and over again in exercises that include any right triangle.

It is calculated by multiplying the two sides that form the right angle (called legs) and dividing the result by 2.

A - area of a new right triangle

Detailed explanation

Practice Area of a right triangle

Test your knowledge with 27 quizzes

Calculate the area of the triangle using the data in the figure below.

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Examples with solutions for Area of a right triangle

Step-by-step solutions included
Exercise #1

Calculate the area of the right triangle below:

101010666888AAACCCBBB

Step-by-Step Solution

Due to the fact that AB is perpendicular to BC and forms a 90-degree angle,

it can be argued that AB is the height of the triangle.

Hence we can calculate the area as follows:

AB×BC2=8×62=482=24 \frac{AB\times BC}{2}=\frac{8\times6}{2}=\frac{48}{2}=24

Answer:

24 cm²

Video Solution
Exercise #2

Calculate the area of the triangle ABC using the data in the figure.

121212888999AAABBBCCCDDD

Step-by-Step Solution

First, let's remember the formula for the area of a triangle:

(the side * the height that descends to the side) /2

 

In the question, we have three pieces of data, but one of them is redundant!

We only have one height, the line that forms a 90-degree angle - AD,

The side to which the height descends is CB,

Therefore, we can use them in our calculation:

CB×AD2 \frac{CB\times AD}{2}

8×92=722=36 \frac{8\times9}{2}=\frac{72}{2}=36

Answer:

36 cm²

Video Solution
Exercise #3

What is the area of the triangle in the drawing?

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Step-by-Step Solution

First, we will identify the data points we need to be able to find the area of the triangle.

the formula for the area of the triangle: height*opposite side / 2

Since it is a right triangle, we know that the straight sides are actually also the heights between each other, that is, the side that measures 5 and the side that measures 7.

We multiply the legs and divide by 2

5×72=352=17.5 \frac{5\times7}{2}=\frac{35}{2}=17.5

Answer:

17.5

Video Solution
Exercise #4

Calculate the area of the following triangle:

444555AAABBBCCCEEE

Step-by-Step Solution

The formula for calculating the area of a triangle is:

(the side * the height from the side down to the base) /2

That is:

BC×AE2 \frac{BC\times AE}{2}

We insert the existing data as shown below:

4×52=202=10 \frac{4\times5}{2}=\frac{20}{2}=10

Answer:

10

Video Solution
Exercise #5

Calculate the area of the following triangle:

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Step-by-Step Solution

The formula for the area of a triangle is

A=hbase2 A = \frac{h\cdot base}{2}

Let's insert the available data into the formula:

(7*6)/2 =

42/2 =

21

Answer:

21

Video Solution

Frequently Asked Questions

What is the formula for finding the area of a right triangle?

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The area of a right triangle is calculated by multiplying the two legs (sides that form the right angle) and dividing by 2. The formula is: Area = (leg₁ × leg₂) ÷ 2.

How do you find the area of a triangle when you know the base and height?

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Use the formula Area = (base × height) ÷ 2. The height must be perpendicular to the base. This formula works for all triangles, not just right triangles.

Can you find a missing leg length if you know the area and one leg of a right triangle?

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Yes, rearrange the area formula to solve for the unknown leg. If Area = (leg₁ × leg₂) ÷ 2, then unknown leg = (2 × Area) ÷ known leg.

What are the most common mistakes when calculating triangle area?

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Common errors include: 1) Forgetting to divide by 2, 2) Using the hypotenuse instead of legs in right triangles, 3) Not ensuring the height is perpendicular to the base, 4) Mixing up units in the final answer.

How do you solve triangle area problems with percentages?

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Convert percentages to decimals first, then apply them to find new measurements. For example, if one leg is 33⅓% greater than another, multiply the original by 1.333 to find the new length.

What units should I use for triangle area answers?

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Area is always measured in square units (cm², m², in², etc.). If the sides are given in centimeters, the area will be in square centimeters (cm²).

How do you check if your triangle area calculation is correct?

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Verify by: 1) Double-checking your multiplication and division, 2) Ensuring you used the correct measurements, 3) Confirming your answer has square units, 4) Using an alternative method if possible.

Can the same triangle have different area calculations depending on which side is the base?

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No, a triangle has only one area value. However, you can use different base-height combinations that will give the same result when calculated correctly using Area = (base × height) ÷ 2.

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