Question

Given that the three angles of a quadrilateral are ${80}^{\circ }$,${100}^{\circ }$ and ${130}^{\circ }$, the fourth angle will be .

• A. ${50}^{\circ }$
• B. ${80}^{\circ }$
• C. ${60}^{\circ }$

Answer 1

The correct option is A ${50}^{\circ }$

The sum of four angles of a quadrilateral is ${360}^{\circ }$.
Let the fourth angle which is unknown be $x$.
By the angle sum property,
${80}^{\circ }$+${100}^{\circ }$+${130}^{\circ }$+ $x$ = ${360}^{\circ }$
$\Rightarrow$${310}^{\circ }$+ $x$ = ${360}^{\circ }$
$\Rightarrow$$x$ = ${50}^{\circ }$