Page 111 - TB_6B

Activity 2 Sum of the Interior Angles of a Quadrilateral

Find the sum of the interior angles of a quadrilateral.

Method 1 Divide quadrilateral ABCD into 4 pieces as shown below.
Place the angles together so that the 4 angles meet at
1 vertex. Find the sum of the angles.

AD 14
14 23

23

BC
What is the sum of the interior angles?

Method 2 Divide the quadrilateral ABCD into 2 triangles as shown
below. Find the sum of the interior angles using the
2 triangles.

AD

BC
(sum of interior angles of a quadrilateral)
= (sum of interior angles of a triangle) 2
=2
=
The sum of the interior angles of a quadrilateral is .

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