Question

Find the angle, which is two-third of its supplement.

• A. 42°
• B. 52°
• C. 62°
• D. 72°

Answer 1

The correct option is D 72°

Let the required angle be $x°$.
Its supplement will be
$(180-x)°.$

To find: The angle which is two-third of its supplement.

So,
$\frac{2}{3}(180-x)=x$
$\frac{2}{3}\times 180-\frac{2}{3}x=x$
$120-\frac{2}{3}x=x$
$120=x+\frac{2}{3}x$
$\frac{5}{3}x=120$
$x=120\times \frac{3}{5}$
$\Rightarrow x={72}^o$
The required angle is ${72}^o$.