In a quadrilateral ABCD, the angles A, B, C and D are in ratio 1:2:3:4. Find the measure of each angle of the quadrilateral. 
 
                Answer: 
            
        ∠A = 36°, ∠B = 72°, ∠C = 108°, ∠D = 144°
- Let's assume x is the common factor of the angles of the quadrilateral.
 According to the question, the angles A, B, C and D are in ratio 1:2:3:4.
 Therefore,
 ∠A = 1x,
 ∠B = 2x,
 ∠C = 3x and
 ∠D = 4x.
- We know that the sum of all interior angles of a quadrilateral is equal to 360°.
 Therefore, ∠A + ∠B + ∠C + ∠D = 360°
 ⇒ 1x + 2x + 3x + 4x = 360°
 ⇒ 10x = 360
 ⇒ x =360 10 
 ⇒ x = 36
- Hence, ∠A = 1x = 1 × 36 = 36°,
 ∠B = 2x = 2 × 36 = 72°,
 ∠C = 3x = 3 ×36 = 108° and
 ∠D = 4x = 4 × 36 = 144°.
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