Find the angle whose supplement is four times its complement.

[ 2 marks ]

Sol:

Let the measure of the required angle be x°.

Then, measure of its complement = (90° – x)

And, measure of its supplement= (180° – x)

[ 1 mark ]

Therefore,

(180° – x) = 4(90° – x)

180° – x = 360° – 4x

3x = 180°

x = 60°

Hence, the measure of the required angle is 60°.
[ 1 mark ]