In quadrilateral ABCD, the bisectors of ∠A and ∠B meet at a point P inside the quadrilateral. If ∠C = 110° and ∠D = 70°, what is the measure of ∠APB?

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A 75°
B 80°
C 90°
D 100°

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Answer: C. 90°

∠A + ∠B + 110° + 70° = 360°, so ∠A + ∠B = 180°.
In triangle APB, ∠APB = 180° - (∠A + ∠B)/2 = 180° - 90° = 90°.

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In quadrilateral ABCD, the bisectors of ∠A and ∠B meet at a point P inside the quadrilateral. If ∠C = 110° and ∠D = 70°, what is the measure of ∠APB?

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