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In a quadrilateral ABCD, ∠C is a right angle, ∠ A is thrice of ∠ B and ∠D is 70°. Find ∠A and ∠B : 1. 120˚ and 80˚2. 110˚ and 90˚3. 150˚ and 50˚4. 140˚ and 60˚ |
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Answer» Correct Answer - Option 3 : 150˚ and 50˚ Given: ABCD is a quadrilateral, ∠C = 90° and ∠D = 70° Concept: The sum of all angles in a quadrilateral is 360°. Calculation: Let assume that ∠B = x So, ∠A = 3x ⇒ The sum of all angles in a quadrilateral is 360°. ⇒ ∠A + ∠B + ∠C + ∠D = 360° ⇒ 3x + x + 90° + 70° = 360° ⇒ 4x + 160˚ = 360° ⇒ 4x = 200° ⇒ x = 50° ∴ ∠B = x = 50° And, ∠A = 3x = 50° × 3 =150° The Correct option is 3 i.e. 150° and 50° |
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