1.

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˚

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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