Examples with solutions for Sum and Difference of Angles: Finding the size of angles in a triangle

Exercise #1

Calculate the size of angle X given that the triangle is equilateral.

XXXAAABBBCCC

Video Solution

Step-by-Step Solution

Remember that the sum of angles in a triangle is equal to 180.

In an equilateral triangle, all sides and all angles are equal to each other.

Therefore, we will calculate as follows:

x+x+x=180 x+x+x=180

3x=180 3x=180

We divide both sides by 3:

x=60 x=60

Answer

60

Exercise #2

ABC is an equilateral triangle.8X8X8XAAABBBCCCCalculate X.

Video Solution

Step-by-Step Solution

Since this is an equilateral triangle, all angles are also equal.

As the sum of angles in a triangle is 180 degrees, each angle is equal to 60 degrees. (180:3=60)

From this, we can conclude that: 60=8x 60=8x

Let's divide both sides by 8:

608=8x8 \frac{60}{8}=\frac{8x}{8}

7.5=x 7.5=x

Answer

7.5

Exercise #3

Below is an equilateral triangle.

Calculate X.

X+5X+5X+5AAABBBCCC

Video Solution

Step-by-Step Solution

Since in an equilateral triangle all sides are equal and all angles are equal. It is also known that in a triangle the sum of angles is 180°, we can calculate X in the following way:

X+5+X+5+X+5=180 X+5+X+5+X+5=180

3X+15=180 3X+15=180

3X=18015 3X=180-15

3X=165 3X=165

Let's divide both sides by 3:

3X3=1653 \frac{3X}{3}=\frac{165}{3}

X=55 X=55

Answer

55

Exercise #4

What type of triangle appears in the drawing?

606060

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle equals 180 degrees.

Let's calculate alpha in the following way:

60+α+α2=180 60+\alpha+\frac{\alpha}{2}=180

60+112α=180 60+1\frac{1}{2}\alpha=180

112α=18060 1\frac{1}{2}\alpha=180-60

112α=120 1\frac{1}{2}\alpha=120

Let's divide both sides by 1.5:

α=80 \alpha=80

Now we can calculate the remaining angle in the triangle:

α2=802=40 \frac{\alpha}{2}=\frac{80}{2}=40

So in the triangle we have 3 angles: 60, 80, 40

All of them are less than 90 degrees, therefore all angles are acute angles and the triangle is an acute triangle.

Answer

Acute triangle

Exercise #5

What type of triangle appears in the drawing?

XXX3X3X3X5X5X5X

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle equals 180 degrees.

Let's calculate X in the following way:

3x+5x+x=180 3x+5x+x=180

9x=180 9x=180

Let's divide both sides by 9:

x=20 x=20

Now let's calculate the angles:

3x=3×20=60 3x=3\times20=60

5x=5×20=100 5x=5\times20=100

This means that in the triangle we have 3 angles: 20, 60, 100

Since we have one angle that is greater than 90 degrees, meaning an obtuse angle, this is an obtuse triangle.

Answer

Obtuse triangle

Exercise #6

What type of triangle appears in the drawing?

ααα303030101010

Video Solution

Step-by-Step Solution

To determine which type of triangle we are dealing with, let's calculate angle alpha based on the fact that the sum of angles in a triangle is 180 degrees.

α=1803010=140 \alpha=180-30-10=140

Since alpha is equal to 140 degrees, the triangle is an obtuse triangle.

Answer

Obtuse triangle

Exercise #7

Find the measure of the angle α \alpha

100100100AAABBBCCC90

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180.

Therefore, we will use the formula:

A+B+C=180 A+B+C=180

Let's input the known data:

100+α+90=180 100+\alpha+90=180

190+α=180 190+\alpha=180

α=180190 \alpha=180-190

We should note that it's not possible to get a negative result, and therefore there is no solution.

Answer

There is no possibility of resolving

Exercise #8

Find the size of angle α \alpha .

27.727.727.7AAABBBCCC41

Video Solution

Step-by-Step Solution

First let's remember that the sum of the angles in a triangle is equal to 180 degrees.

Therefore, we can use the formula:

A+B+C=180 A+B+C=180

Then we will substitute in the known data:

α+27.7+41=180 \alpha+27.7+41=180

α+68.7=180 \alpha+68.7=180

Finally, we will move the variable to the other side while maintaining the appropriate sign:

α=18068.7 \alpha=180-68.7

α=111.3 \alpha=111.3

Answer

111.3

Exercise #9

Find the measure of the angle α \alpha

696969AAABBBCCC23

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

Therefore, we will use the following formula:

A+B+C=180 A+B+C=180

Now let's input the known data:

α+69+23=180 \alpha+69+23=180

α+92=180 \alpha+92=180

We'll move the term to the other side and keep the appropriate sign:

α=18092 \alpha=180-92

α=88 \alpha=88

Answer

88

Exercise #10

Find the measure of the angle α \alpha

808080AAABBBCCC55

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

Therefore, we will use the following formula:

A+B+C=180 A+B+C=180

Now let's input the known data:

80+55+α=180 80+55+\alpha=180

135+α=180 135+\alpha=180

We'll move the term to the other side and keep the appropriate sign:

α=180135 \alpha=180-135

α=45 \alpha=45

Answer

45

Exercise #11

Find the measure of the angle α \alpha

949494AAABBBCCC92

Video Solution

Step-by-Step Solution

It is known that the sum of angles in a triangle is 180 degrees.

Since we are given two angles, we can calculate a a

94+92=186 94+92=186

We should note that the sum of the two given angles is greater than 180 degrees.

Therefore, there is no solution possible.

Answer

There is no possibility of resolving

Exercise #12

Find the measure of the angle α \alpha

120120120AAABBBCCC27

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

Therefore, we will use the following formula:

A+B+C=180 A+B+C=180

Now let's input the known data:

120+27+α=180 120+27+\alpha=180

147+α=180 147+\alpha=180

We'll move the term to the other side and keep the appropriate sign:

α=180147 \alpha=180-147

α=33 \alpha=33

Answer

33

Exercise #13

Find the measure of the angle α \alpha

505050AAABBBCCC50

Video Solution

Step-by-Step Solution

Recall that the sum of angles in a triangle equals 180 degrees.

Therefore, we will use the following formula:

A+B+C=180 A+B+C=180

Now let's insert the known data:

α+50+50=180 \alpha+50+50=180

α+100=180 \alpha+100=180

We will simplify the expression and keep the appropriate sign:

α=180100 \alpha=180-100

α=80 \alpha=80

Answer

80

Exercise #14

Tree angles have the sizes:

90°, 60°, and 40.

Is it possible that these angles are in a triangle?

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

We'll add the three angles to see if their sum equals 180:

90+60+40=190 90+60+40=190

Therefore, these cannot be the values of angles in any triangle.

Answer

Yes.

Exercise #15

Three angles measure as follows: 60°, 50°, and 70°.

Is it possible that these are angles in a triangle?

Video Solution

Step-by-Step Solution

Recall that the sum of angles in a triangle equals 180 degrees.

Let's add the three angles to see if their sum equals 180:

60+50+70=180 60+50+70=180

Therefore, it is possible that these are the values of angles in some triangle.

Answer

Possible.

Exercise #16

Tree angles have the sizes 94°, 36.5°, and 49.5. Is it possible that these angles are in a triangle?

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

We'll add the three angles to see if their sum equals 180:

94+36.5+49.5=180 94+36.5+49.5=180

Therefore, these could be the values of angles in some triangle.

Answer

Possible.

Exercise #17

Tree angles have the sizes:

31°, 122°, and 85.

Is it possible that these angles are in a triangle?

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

We'll add the three angles to see if their sum equals 180:

31+122+85=238 31+122+85=238

Therefore, these cannot be the values of angles in any triangle.

Answer

Impossible.

Exercise #18

Tree angles have the sizes:

76°, 52°, and 52°.

Is it possible that these angles are in a triangle?

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

We will add the three angles to find out if their sum equals 180:

76+52+52=180 76+52+52=180

Therefore, these could be the values of angles in some triangle.

Answer

Yes.

Exercise #19

Tree angles have the sizes:

69°, 93°, and 81.

Is it possible that these angles are in a triangle?

Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

We'll add the three angles to see if their sum equals 180:

69+81+93=243 69+81+93=243

Therefore, these cannot be the values of angles in any triangle.

Answer

No.

Exercise #20

Tree angles have the sizes:

50°, 41°, and 81.

Is it possible that these angles are in a triangle?


Video Solution

Step-by-Step Solution

Let's remember that the sum of angles in a triangle is equal to 180 degrees.

We'll add the three angles to see if their sum equals 180:

50+41+81=172 50+41+81=172

Therefore, these cannot be the values of angles in any triangle.

Answer

Impossible.