Question

In quadrilateral ABCD m ZA-90° m / C = 50° and m B = m 2D. Find the degree measure of Z B.

Answer 1

The sum of the internal angles in a quadrilateral is equal to 360, therefore:

$\begin{gathered} \angle A+\angle B+\angle C+\angle D=360 \\ 90+\angle B+50+\angle B=360 \\ 140+2\angle B=360 \\ 2\angle B=360-140 \\ 2\angle B=220 \\ \angle B=\frac{220}{2} \\ \angle B=110 \end{gathered}$