A quadrilateral has three acute angles, each measure 80°. what is the measure of the fourth angle?

A quadrilateral has three acute angles each measures 80°. What is the measure of the fourth angle?

\[\text{ Let x be the fourth angle }  . \]

\[ \text{ Since, the sum of all angles of a quadrilateral is }  360°, \text{ we have: }  \]

\[80° + 80° + 80° + x = 360° \]

\[ \Rightarrow 240° + x = 360° \]

\[ \Rightarrow x = 120° \]

\[ \therefore \text{ The fourth angle is } 120° .\]

Concept: Concept of Quadrilaterals - Sides, Adjacent Sides, Opposite Sides, Angle, Adjacent Angles and Opposite Angles

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