Question
In Fig. x + y =

  1. 270º
  2. 230º
  3. 210º
  4. 190º

Answer

  1. 230º

Solution:

$\triangle\text{ACO}$

$\angle\text{ACO}+\angle\text{COA}+\angle\text{COA}=180^\circ$

Now, $\angle\text{OAC}=180^\circ-\text{x}^\circ$

$\Rightarrow80^\circ+40^\circ+180^\circ-\text{x}^\circ=180^\circ$

$\Rightarrow\text{x}^\circ=120^\circ$

$\angle\text{BOD}=\angle\text{COA}=40^\circ$ (Opposite angles)

$\angle\text{BDO}=70^\circ$

In $\triangle\text{OBD},$

$\angle\text{OBD}=180^\circ-40^\circ-70^\circ=70^\circ$

Also, $\text{y}^\circ=180^\circ-\angle\text{OBD}=180^\circ-70^\circ=110^\circ$

$\Rightarrow\text{x}^\circ+\text{y}^\circ=120^\circ+110^\circ=230^\circ$

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