Question

Find the value of x in the following figure if $l||manda||b$.

• A. ${80}^{\circ }$
• B. ${100}^{\circ }$
• C. ${120}^{\circ }$
• D. ${40}^{\circ }$

Answer 1

The correct option is B ${100}^{\circ }$

(a) Given, $a\parallel b$ and $l\parallel m$

Mark an angle 1 in the figure.

$\angle 1={80}^{\circ }$ [Since 'a' is parallel to 'b', they are corresponding angles]

Now,

$\angle 1+\angle x={180}^{\circ }$ [Since $l\parallel m,angle1and\angle x$ are cointerior angles]

$\Rightarrow \angle x={180}^{\circ }-{80}^{\circ }$

$\Rightarrow \angle x={100}^{\circ }$