MCQ
In Fig. $a = 40^\circ .$ The value of $b$ is:
- ✓$20^\circ$
- B$24^\circ$
- C$36^\circ$
- D$120^\circ$
✓
Answer
Correct option: A.
$20^\circ$
From the given figure it is clear that,
$2a + 5b = 180^\circ [$Liner pair$]$
$\Rightarrow 2 \times 40^\circ + 5b$ $180^\circ [\because a = 40^\circ ]$
$\Rightarrow 80^\circ + 5b = 180^\circ $
$\Rightarrow 5b = 180^\circ - 80^\circ $
$\Rightarrow 5b = 100^\circ $
$\Rightarrow\text{b}=\frac{100^\circ}{5}$
$\Rightarrow b = 20^\circ $
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