Question

`square` ABCD is a parallelogram. The ratio of `angle`A and `angle`B of this parallelogram is 5 : 4. Find the measure of `angle`B.

Answer 1

Quadrilateral ABCD is a parallelogram.

Let the measure of `angle`A and `angle` B be 5xº and 4xº, respectively.

Now,

`angle` A + `angle` B = 180º    ...(Adjacent angles of a parallelogram are supplementary)

∴5xº + 4xº = 180º

⇒ 9xº = 180º

⇒ xº = 20º

∴ Measure of `angle`B = 4xº = 4 × 20º = 80º

Thus, the measure of `angle`B is 80º.