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

Here, $ABCD$ is a parallelogram.

Let the measure of $\angle A$ and $\angle B$ be $5x$ and $4x$.

We know that in parallelogram sum of measure of adjacent angles is supplementary.

$\therefore$ $\angle A+\angle B={180}^o$

$\Rightarrow$ $5x+4x={180}^o$

$\Rightarrow$ $9x={180}^o.$

$\Rightarrow$ $x={20}^o.$

Measure of $\angle B=4x=4\times {20}^o={80}^o.$