Question

The three angles of a quadrilateral are 80⁰,70⁰ and 120⁰. The fourth angle is

  (a) 110⁰
  (b) 100⁰
  (c) 90⁰
  (d) 80⁰


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Answer 1

Answer:

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Step-by-step explanation:

Sum of Angles in a Quadrilateral = 360°

Let the fourth angle be as x

80° + 70° + 120° + x° = 360°

270° + x° = 360°

x° = 360° - 270° = 90°

Option (c) 90°

Answer 2

Concept:

This question is based on the concept of quadrilaterals.

Quadrilateral is a 2 dimensional, closed  shape having four straight sides.

The sum of all interior angle of a quadrilateral  adds to  $360^{0}$

Given:

Three angles of quadrilateral are $80^{0}, 70^{0} and 120^{0}$

To find :

The fourth angle of the quadrilateral.

Solution:

Let the fourth angle of quadrilateral be x.

Sum of all four angles of quadrilateral = $360^{0}$

                             $80^{0}+70^{0} + 120^{0}+x =360^{0}$

                                                $270^{0}+x=360^{0}$

                                                            $x=360^{0}-270^{0}$

                                                            $x=90^{0}$

Hence, the fourth angle is $90^{0}$

Option (c) is correct choice.