Test your understanding of finding missing angles in a triangle.

Try to answer the questions before checking the answers at the bottom of the page.

Question 1

A triangle has angles:

\(60^\circ, x, 30^\circ\)

Find \(x\).

A) \(80^\circ\)
B) \(90^\circ\)
C) \(100^\circ\)

Question 2

A triangle has angles:

\(x, 90^\circ, 40^\circ\)

Find \(x\).

A) \(40^\circ\)
B) \(50^\circ\)
C) \(60^\circ\)

Question 3

A triangle has angles:

\(50^\circ, 100^\circ, x\)

Find \(x\).

A) \(20^\circ\)
B) \(30^\circ\)
C) \(40^\circ\)

Question 4

A triangle has angles:

\(x, 60^\circ, x\)

Find \(x\).

A) \(50^\circ\)
B) \(60^\circ\)
C) \(70^\circ\)

Question 5

A triangle has angles:

\(x, 3x, 2x\)

Find \(x\).

A) \(20^\circ\)
B) \(30^\circ\)
C) \(40^\circ\)

Question 6

A triangle has angles:

\(70^\circ,\quad 45^\circ,\quad x\)

Find \(x\).

A) \(55^\circ\)
B) \(75^\circ\)
C) \(65^\circ\)

Question 7

A triangle has angles:

\(x,\quad x,\quad 40^\circ\)

Find \(x\).

A) \(70^\circ\)
B) \(60^\circ\)
C) \(80^\circ\)

Question 8

A triangle has angles:

\(x,\quad x+20^\circ,\quad 80^\circ\)

Find \(x\).

A) \(30^\circ\)
B) \(40^\circ\)
C) \(50^\circ\)

Question 9

A triangle has angles:

\(2x,\quad 3x,\quad 5x\)

Find \(x\).

A) \(15^\circ\)
B) \(20^\circ\)
C) \(18^\circ\)

Question 10

A right triangle has one acute angle equal to \(35^\circ\).

What is the other acute angle?

A) \(55^\circ\)
B) \(45^\circ\)
C) \(65^\circ\)

Answers

1. B – \(90^\circ\)
2. B – \(50^\circ\)
3. B – \(30^\circ\)
4. B – \(60^\circ\)
5. B – \(30^\circ\)
6. C – \(65^\circ\)
7. A – \(70^\circ\)
8. B – \(40^\circ\)
9. C – \(18^\circ\)
10. A – \(55^\circ\)

Practice

• More Examples

• Take the Quiz (Current page)

Continue Learning

1. Sum of Angles of a Triangle is 180° (Proof)
2. Find the Missing Angle of a Triangle

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