Triangles and Angles

Do you like triangles?

Triangles and Angles

This Math quiz is called 'Triangles and Angles' and it has been written by teachers to help you if you are studying the subject at middle school. Playing educational quizzes is a fabulous way to learn if you are in the 6th, 7th or 8th grade - aged 11 to 14.

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A triangle is a geometric form created by connecting three straight lines. Where each line connects or intersects you get an angle. A triangle will have three angles.

An angle is measured in degrees (°). The degree of an angle runs between 0° and 180°.

Both triangles and angles are classified into three different types: acute, right and obtuse

TRIANGLES:

An acute triangle is a triangle where all three angles measure less than 90°.
Example: Angle A is 47°, Angle B is 39°, and Angle C is 12°

A right triangle is a triangle where at least one of the angles measures exactly 90°.
Example: Angle A is 68°, Angle B is 51°, and Angle C is 90°

An obtuse triangle is a triangle where at least one of the angles measures more than 90°.
Example: Angle A is 22°, Angle B is 138°, and Angle C is 44°

ANGLES:

An acute angle is an angle that measures less than 90°.
A right angle is an angle that measures exactly 90°.
An obtuse angle is an angle that measures more than 90°.

How to find the missing degree of an angle in a triangle is easy. You need to subtract the known from the sum of the three angles. If Angle A is 92° and Angle B is 31° what would Angle C be? You simply start with Angle A and subtract Angle B to get Angle C as follows:

92° - 31° = 61°

Angle C is 61° - correct? Well, not exactly because, remember, we are measuring the degree of an angle of a triangle. The three angles of a triangle must always be equal to a total of 180° (the sum of all three angles). So we need to first add together the known angles, here it is 92° and 31° and then we subtract that answer from the total of 180° as follows:

92° + 31° = 123°
180° - 123° = 57°
92° + 31° + 57° = 180°
Angle C = 57°

1.
If Angle A is 60° and Angle B is 45°, what type of an angle would Angle C be?
Straight
Obtuse
Acute
Right
60° + 45° = 105°
180° - 105° = 75°
Angle C is 75° and because it is less than 90° it makes it an acute angle. Answer (c) is the correct answer
2.
What is Angle C if Angle A is 33° and Angle B is 17°?
147°
163°
50°
130°
33° + 17° = 50°
180° - 50° = 130°
Angle C is 130° so Answer (d) is the correct answer
3.
If Angle A is 72° and Angle B is 33°, what type of an angle would Angle C be in a triangle?
Right
Straight
Obtuse
Acute
72° + 33° = 105°
180° - 105° = 75°
Angle C is 75° and because it is less than 90° it is an acute angle. Answer (d) is the correct answer
4.
If Angle A is 68° and Angle B is 22°, what type of an angle would Angle C be?
Acute
Right
Straight
Obtuse
68° + 22° = 90°
180° - 90° = 90°
Angle C is 90° making it a right angle so Answer (b) is the correct answer
5.
What type of a triangle do you have if Angle A is 28°, Angle B is 62°, and Angle C is 90°?
Right
Acute
Obtuse
Straight
When at least one angle measures exactly 90°, it is a right triangle. Answer (a) is correct
6.
If Angle A is 49° and Angle B is 27°, what type of an angle would Angle C be?
Obtuse
Right
Acute
Straight
49° + 27° = 76°
180° - 76° = 104°
Angle C is 104° and because it is greater than 90° it is an obtuse. Answer (a) is the correct answer
7.
What is Angle C of a triangle if Angle A is 67° and Angle B is 59°?
126°
54°
113°
121°
67° + 59° = 126°
180° - 126° = 54°
67 + 59 + 54 = 180°
Angle C is 54° so Answer (b) is correct
8.
What type of a triangle do you have if Angle A is 56°, Angle B is 111°, and Angle C is 13°?
Straight
Right
Acute
Obtuse
When at least one angle is more than 90°, it is an obtuse triangle. Answer (d) is correct
9.
What type of a triangle do you have if Angle A is 77°, Angle B is 82°, and Angle C is 21°?
Acute
Right
Obtuse
Straight
When all three angles are less than 90°, it is an acute triangle. Answer (a) is correct
10.
What type of triangle do you have if Angle A is 13°, Angle B is 45°, and Angle C is 122°?
Straight
Obtuse
Right
Acute
When at least one angle is more than 90°, it is an obtuse triangle. Answer (b) is correct
Author:  Christine G. Broome

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