Question

If two angles of a triangle are 40 degrees and 80 degrees, then the measure of the third angle is ____ degrees.

Answer 1

Missing Angles

`\rule{300}{4}`

Let's solve the problem given to us today! The problem is:

`\mapsto\quad\textsf{\textbf{If two angles in a triangle are 40 degrees and 80 degrees, find the}}\\\textsf{\textbf{measure of the third angle.}}`

Main Idea :

• The sum of the three angles in a triangle is always 180°.

So, we can find the missing angle by setting up an equation, where x = the missing angle :

• 
  `\textsf{\textbf{40 + 80 + x = 180}}`

Combine the like terms

• 
  `\textsf{\textbf{120 + x = 180}}`

Subtract 120 from both sides:

• 
  `\textsf{\textbf{x = 60}}`

Therefore, the missing angle is 60 degrees.

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Answer 2

60°

Explanation:

By Applying Angle Sum Property of a ∆.

Angle A + B + C = 180°

40 + 80 + x = 180

x = 180 - 120

x = 60°

the measure of third angle is 60°.