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Question
In the given figure : ∠b = 2a + 15 and ∠c = 3a + 5; find the values of b and c.
Solution
∵ Sum of angles of quadrilateral = 360°
70° + a + 2a + 15 + 3a + 5 = 360°
6a + 90° = 360°
6a = 270°
a = 45°
∴ b = 2a + 15 = 2 x 45 + 15 = 105°
c = 3a + 5 = 3 x 45 + 5 = 140°
Hence ∠b and ∠c are 105° and 140°
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