Question 12 Marks
A quadrilateral has three acute angles each measures $80^\circ .$ What is the measure of fourth angle$?$
Answer
View full question & answer→Sum of four angles of a quadrilateral $= 360^\circ $
Sum of three angles having each angle equal to $80^\circ = 80^\circ \times 3 = 240^\circ $
Let fourth angle $= x$ Then, $240^\circ + x = 360^\circ $
$\Rightarrow x^\circ = 360^\circ – 240^\circ $
$ \Rightarrow x^\circ = 120^\circ $
Fourth angle $= 120^\circ $
Sum of three angles having each angle equal to $80^\circ = 80^\circ \times 3 = 240^\circ $
Let fourth angle $= x$ Then, $240^\circ + x = 360^\circ $
$\Rightarrow x^\circ = 360^\circ – 240^\circ $
$ \Rightarrow x^\circ = 120^\circ $
Fourth angle $= 120^\circ $

