Question

Question 4
In the figure, if $\angle ABC={20}^{\circ }$, then $\angle AOC$ is equal to

(A) ${20}^{\circ }$
(B) ${40}^{\circ }$
(C) ${60}^{\circ }$
(D) ${10}^{\circ }$

Answer 1

The answer is B.
Given, $\angle ABC={20}^{\circ }$
We know that, angle subtended at the centre by an arc is twice the angle subtended by it at the remaining part of the circle.
$\angle AOC=2\angle ABC=2\times {20}^{\circ }={40}^{\circ }$