Similarity Ratio Practice Problems with Step-by-Step Solutions

Master similarity ratios with guided practice problems. Learn to calculate ratios between corresponding sides of similar triangles and polygons through examples.

📚What You'll Master in This Practice Session
  • Calculate similarity ratios by dividing corresponding sides of similar figures
  • Identify corresponding sides in similar triangles and polygons accurately
  • Apply the four-step method to find similarity ratios systematically
  • Solve real-world problems involving similar shapes and scale factors
  • Distinguish between similarity ratios and congruent figure relationships
  • Work with fractional and decimal similarity ratios confidently

Understanding The Ratio of Similarity

Complete explanation with examples

What is the similarity ratio?

The similarity ratio is the constant difference between the corresponding sides of the two shapes.
That is, if the similarity ratio is 3 3 , we know that each side of the large triangle is 3 3 times larger than that of the small triangle.

How do we calculate the similarity ratio?

The calculation of the similarity ratio is divided into several steps that must be performed:

  1. First we must know that we are dealing with similar triangles or polygons.
  2. We must know how to identify the corresponding sides in each of the triangles or polygons.
  3. We need to know the sizes of a pair of equal sides.
  4. We must divide the size of one side by the size of the other side.

The result obtained is actually the similarity ratio.

A1 - How do we calculate the similarity ratio

Detailed explanation

Practice The Ratio of Similarity

Test your knowledge with 19 quizzes

5.213125 The triangle above are similar.

What is the perimeter of the blue triangle?

Examples with solutions for The Ratio of Similarity

Step-by-step solutions included
Exercise #1

AAABBBCCCDDDEEE60°30°30°60°ΔACBΔBED ΔACB∼ΔBED

Choose the correct answer.

Step-by-Step Solution

First, let's look at angles C and E, which are equal to 30 degrees.

Angle C is opposite side AB and angle E is opposite side BD.

ABDB \frac{AB}{DB}

Now let's look at angle B, which is equal to 90 degrees in both triangles.

In triangle ABC the opposite side is AC and in triangle EBD the opposite side is ED.

ACED \frac{AC}{ED}

Let's look at angles A and D, which are equal to 60 degrees.

Angle A is the opposite side of CB, angle D is the opposite side of EB

CBEB \frac{CB}{EB}

Therefore, from this it can be deduced that:

ABBD=ACED \frac{AB}{BD}=\frac{AC}{ED}

And also:

CBED=ABBD \frac{CB}{ED}=\frac{AB}{BD}

Answer:

Answers a + b are correct.

Video Solution
Exercise #2

AAABBBCCCMMMNNN36 What is the ratio between the sides of the triangles ΔABC and ΔMNA?

Step-by-Step Solution

From the data in the drawing, it seems that angle M is equal to angle B

Also, angle A is an angle shared by both triangles ABC and AMN

That is, triangles ABC and AMN are similar respectively according to the angle-angle theorem.

According to the letters, the sides that are equal to each other are:

ABAM=BCMN=ACAN \frac{AB}{AM}=\frac{BC}{MN}=\frac{AC}{AN}

Now we can calculate the ratio between the sides of the given triangles:

MN=3,BC=6 MN=3,BC=6 63=2 \frac{6}{3}=2

Answer:

BCMN=2 \frac{BC}{MN}=2

Video Solution
Exercise #3

What is the ratio of similarity between the triangles shown in the diagram below?

AAABBBDDDCCCEEE

Step-by-Step Solution

From the drawing it appears that angle E equals angle A

Since angle D equals 90 degrees, its adjacent angle also equals 90 degrees.

In other words, angle D1 equals angle D2 and both equal 90 degrees.

Since we have two pairs of equal angles, the triangles are similar.

Also angle B equals angle C

Now let's write the similar triangles according to their corresponding angle letters:

ABC=ECD ABC=ECD

Let's write the ratio of sides according to the corresponding letters of the similar triangles:

ABEC=ADED=BDCD \frac{AB}{EC}=\frac{AD}{ED}=\frac{BD}{CD}

Answer:

ABEC=ADED=BDCD \frac{AB}{EC}=\frac{AD}{ED}=\frac{BD}{CD}

Video Solution
Exercise #4

Triangle DFE is similar to triangle ABC.

Calculate the length of FE.8y8y8y7m7m7m9y9y9yAAABBBCCCDDDEEEFFF

Step-by-Step Solution

Let's look at the order of letters of the triangles that match each other and see the ratio of the sides.

We will write accordingly:

Triangle ABC is similar to triangle DFE

The order of similarity ratio will be:

ABDF=BCFE=ACDE \frac{AB}{DF}=\frac{BC}{FE}=\frac{AC}{DE}

Now let's insert the existing data we have in the diagram:

8y9y=7mFE \frac{8y}{9y}=\frac{7m}{FE}

Let's reduce y and we get:

89FE=7m \frac{8}{9}FE=7m

FE=98×7m FE=\frac{9}{8}\times7m

FE=778m FE=7\frac{7}{8}m

Answer:

778m 7\frac{7}{8}m

Video Solution
Exercise #5

BC is parallel to DE.

Fill in the gap:

AD=AEAC \frac{AD}{}=\frac{AE}{AC}

AAABBBCCCDDDEEE

Step-by-Step Solution

Since we are given that line BC is parallel to DE

Angle E equals angle C and angle D equals angle B - corresponding angles between parallel lines are equal.

Now let's observe that angle D is opposite to side AE and angle B is opposite to side AC, meaning:

AEAC \frac{AE}{AC}

Now let's observe that angle E is opposite to side AD and angle C is opposite to side AB, meaning:

ADAB \frac{AD}{AB}

Answer:

AB

Video Solution

Frequently Asked Questions

What is a similarity ratio and how do you calculate it?

+
A similarity ratio is the constant factor between corresponding sides of two similar figures. To calculate it, divide the length of a side from one figure by the length of the corresponding side from the other figure. For example, if triangle ABC has side AB = 6 and similar triangle DEF has corresponding side DE = 3, the similarity ratio is 6/3 = 2.

How do you identify corresponding sides in similar triangles?

+
Corresponding sides are opposite to equal angles in similar triangles. First, identify which angles are equal between the triangles. Then, the sides opposite these equal angles are corresponding sides. For instance, if angle A equals angle D, then the sides opposite these angles (BC and EF) are corresponding.

What are the steps to find similarity ratio between two polygons?

+
Follow these four steps: 1) Confirm the figures are similar, 2) Identify corresponding sides by matching equal angles, 3) Find the measurements of at least one pair of corresponding sides, 4) Divide one side length by its corresponding side length. The result is your similarity ratio.

Can similarity ratios be fractions or decimals?

+
Yes, similarity ratios can be fractions, decimals, or whole numbers. For example, if a large triangle has a side of 12 units and the corresponding side of a smaller similar triangle is 8 units, the ratio is 12/8 = 3/2 = 1.5. Always express the ratio in its simplest form.

What's the difference between similarity ratio and congruent figures?

+
Similar figures have the same shape but different sizes, with a similarity ratio other than 1. Congruent figures have identical shapes AND sizes, meaning their similarity ratio is exactly 1. All corresponding sides of congruent figures are equal in length.

How do you find missing side lengths using similarity ratios?

+
Once you know the similarity ratio, multiply any known side by the ratio to find the corresponding side in the larger figure, or divide by the ratio to find the corresponding side in the smaller figure. If the ratio is 3 and one side is 4 units, the corresponding side is either 12 units (4×3) or 4/3 units depending on which figure is larger.

What are common mistakes when calculating similarity ratios?

+
Common errors include: mixing up corresponding sides, forgetting to simplify fractions, dividing in the wrong order, and assuming figures are similar without checking angle measures. Always verify that angles are equal before calculating ratios, and double-check which sides actually correspond.

How do similarity ratios apply to real-world problems?

+
Similarity ratios are used in scale drawings, maps, photography, and architecture. For example, if a building blueprint uses a 1:100 scale, every 1 cm on paper represents 100 cm in reality. This similarity ratio helps architects and engineers create accurate scaled representations of actual structures.

More The Ratio of Similarity Questions

Continue Your Math Journey

Topics Learned in Later Sections

Practice by Question Type