Question

If the measure of three angles of a quadrilateral are 100°, 120° and85°,then measure of its fourth angle is:

Answer 1

∠A+ ∠B + ∠C + ∠D = 360°

⇒ 120° + 100°+ 45°+ ∠D = 360°

∠D = 360° – (120° + 100° + 85°)

= 360° -305° = 55°

Hence, the fourth angle of a quadrilateral is 55°.

Answer 2

Answer:

let unknown angle be 'x'

100 +120 + 85 + x =360 [ sum of all the angles in a quadrilateral is 360° ]

305 +x =360

x =360 - 305

=> [ x = 55 ° ]

Step-by-step explanation:

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