Question

If three angles of a quadrlateral are ${76}^{\circ }$, ${104}^{\circ }$ and ${89}^{\circ }$.

Find its fourth angle.

• A. ${93}^{\circ }$
• B. ${51}^{\circ }$
• C. ${91}^{\circ }$
• D. ${61}^{\circ }$

Answer 1

The correct option is C

${91}^{\circ }$

Let the fourth angle be $x$

$\because$ Sum of interior angles of a quadrilateral $={360}^{\circ }$

$\Rightarrow {76}^{\circ }+{104}^{\circ }+{89}^{\circ }+x={360}^{\circ }$

$\Rightarrow x={360}^{\circ }-({76}^{\circ }+{104}^{\circ }+{89}^{\circ })$

$\Rightarrow x=({360}^{\circ }-{269}^{\circ })={91}^{\circ }$