Area of a Triangle Practice Problems & Step-by-Step Solutions

Master triangle area calculations with interactive practice problems. Learn the formula for all triangle types: equilateral, isosceles, scalene, right, and obtuse triangles.

📚What You'll Practice and Master
  • Apply the Area = (Base × Height) ÷ 2 formula to various triangle types
  • Calculate areas of right triangles using legs as base and height
  • Find missing measurements when given triangle area and one dimension
  • Solve real-world problems involving triangular shapes and tiling
  • Use Heron's formula to find area when all three sides are known
  • Work with obtuse triangles where height extends outside the triangle

Understanding Area of a Triangle

Complete explanation with examples

The Formula For Calculating The Area Of A Triangle

The formula for calculating the area of a triangle of any type:

height times base divided by 2 2 .

Area=Base×Height2 Area=\frac{Base\times Height}{2}

Where:

  • Base = any side of the triangle
  • Height = the perpendicular distance (at 90°) from the opposite vertex to the base line (or its extension).

How to find the area of a triangle:

A3 - the general formula for calculating the area of triangles

Detailed explanation

Practice Area of a Triangle

Test your knowledge with 27 quizzes

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

888666AAABBBCCC10

Examples with solutions for Area of a Triangle

Step-by-step solutions included
Exercise #1

Complete the sentence:

To find the area of a right triangle, one must multiply ________________ by each other and divide by 2.

Step-by-Step Solution

To solve this problem, begin by identifying the elements involved in calculating the area of a right triangle. In a right triangle, the two sides that form the right angle are known as the legs. These legs act as the base and height of the triangle.

The formula for the area of a triangle is given by:

A=12×base×height A = \frac{1}{2} \times \text{base} \times \text{height}

In the case of a right triangle, the base and height are the two legs. Therefore, the process of finding the area involves multiplying the lengths of the two legs together and then dividing the product by 2.

Based on this analysis, the correct way to complete the sentence in the problem is:

To find the area of a right triangle, one must multiply the two legs by each other and divide by 2.

Answer:

the two legs

Exercise #2

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 #3

Calculate the area of the following triangle:

4.54.54.5777AAABBBCCCEEE

Step-by-Step Solution

To find the area of the triangle, we will use the formula for the area of a triangle:

Area=12×base×height \text{Area} = \frac{1}{2} \times \text{base} \times \text{height}

From the problem:

  • The length of the base BC BC is given as 7 units.
  • The height from point A A perpendicular to the base BC BC is given as 4.5 units.

Substitute the given values into the area formula:

Area=12×7×4.5 \text{Area} = \frac{1}{2} \times 7 \times 4.5

Calculate the expression step-by-step:

Area=12×31.5 \text{Area} = \frac{1}{2} \times 31.5

Area=15.75 \text{Area} = 15.75

Therefore, the area of the triangle is 15.75 15.75 square units. This corresponds to the given choice: 15.75 15.75 .

Answer:

15.75

Video Solution
Exercise #4

What is the area of the triangle in the drawing?

5557778.68.68.6

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 #5

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

666888AAABBBCCC

Step-by-Step Solution

To calculate the area of the triangle, we will follow these steps:

  • Identify the base, CB, as 6 units.
  • Identify the height, AC, as 8 units.
  • Apply the area formula for a triangle.

Now, let's work through these steps:

The triangle is a right triangle with base CB=6 CB = 6 units and height AC=8 AC = 8 units.

The area of a triangle is determined using the formula:

Area=12×base×height \text{Area} = \frac{1}{2} \times \text{base} \times \text{height}

Substituting the known values, we have:

Area=12×6×8 \text{Area} = \frac{1}{2} \times 6 \times 8

Perform the multiplication and division:

Area=12×48=24 \text{Area} = \frac{1}{2} \times 48 = 24

Therefore, the area of the triangle is 24 24 square units.

Answer:

24

Video Solution

Frequently Asked Questions

What is the formula for finding the area of any triangle?

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The universal formula for triangle area is Area = (Base × Height) ÷ 2. This works for all triangle types - equilateral, isosceles, scalene, right, and obtuse triangles. The height must be perpendicular to the base.

How do you find the area of a right triangle?

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For right triangles, you can use either leg as the base and the other leg as the height since they're perpendicular. Simply multiply the two legs and divide by 2: Area = (leg₁ × leg₂) ÷ 2.

What's different about calculating the area of an obtuse triangle?

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In obtuse triangles, the height often falls outside the triangle when drawn from the obtuse angle. You extend the base line to meet the perpendicular height line, but still use the same formula: Area = (Base × Height) ÷ 2.

When should I use Heron's formula instead of the basic triangle area formula?

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Use Heron's formula when you know all three side lengths but don't know the height. The formula is Area = √[s(s-a)(s-b)(s-c)], where s = (a+b+c)/2 is the semi-perimeter.

How do I find a missing dimension if I know the triangle's area?

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Rearrange the area formula to solve for the unknown. If you need the height: Height = (2 × Area) ÷ Base. If you need the base: Base = (2 × Area) ÷ Height. Always ensure your units are consistent.

What are common mistakes students make when calculating triangle areas?

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Common errors include: 1) Forgetting to divide by 2, 2) Using the wrong measurements as base and height (they must be perpendicular), 3) Misidentifying the height in obtuse triangles, 4) Not converting units consistently.

How can I check if my triangle area calculation is correct?

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Verify your answer by: 1) Ensuring the height is perpendicular to the base, 2) Double-checking your arithmetic, 3) Confirming units are consistent, 4) Estimating if the result seems reasonable for the triangle's size.

What's the relationship between triangle area and squares or rectangles?

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A triangle is exactly half of a parallelogram (including rectangles and squares) with the same base and height. This is why we divide by 2 in the triangle area formula - we're finding half the area of the corresponding parallelogram.

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