Question

In fig. $△ABC$ has $AB=BC,\angle B=x^0,\angle A=(2x-20{)}^0.$ Then, measure of $\angle B\left(indegrees\right)=?$

Answer 1

From fig.,

In $△ABC$,

$\because AB=BC$

$\therefore \angle C=\angle A=(2x-20)°(\because \text{angle oppsite to the equal sides are equal})$

$\angle B=x°$

As we know that sum of all interior angles of a triangle is $180°$.

$\therefore \angle A+\angle B+\angle C=180°$

$\Rightarrow (2x-20)°+x°+(2x-20)°=180°$

$\Rightarrow (5x-40)°=180°$

$\Rightarrow 5x=180°+40°$

$\Rightarrow x=\frac{220}{5}=44°$

$\therefore \angle B=44°$

Hence, the correct answer is 44.