Q15 of 32 Page 67

In Figure 5.73 two straight lines are intersecting each other. In marked angles it ∠1 + ∠2 + ∠3 = 230° the find ∠1 and ∠4.

In the above figure,

∠ a and ∠ 3 form a linear pair and hence their sum has to be 180°.


So ∠ 2 + ∠ 3 = 180°


Given, ∠1 + ∠2 + ∠3 = 230°


∠1 + 180° = 230°


∠ 1 = 230 – 180


∠ 1 = 50°.


∠ 1 + ∠ 2 = 180° as they form linear pair.


So ∠ 2 = 180 – 50


∠ 2 = 130°


So ∠ 4 = ∠ 2 = 130° as they are vertically opposite angles.


So ∠ 1 = 50° and ∠ 4 = 130°.


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