Question

Mark is making a decoration for a rally, using a string of triangular strips. Each strip is an isosceles triangle when flattened out.
( by the way the picture is a triangle that is 70 degrees)

What is the measure of the third angle?

Answer 1

Solution:

Consider the Given Isosceles Triangle

Considering the Possibilities

Case 1. When two equal angles are of 70°

 Let the third angle be x.

Keeping in mind , that sum of Interior angles of Triangle is 180°.

70° + 70° + x= 180°

140° +x= 180°

x= 180°- 140°

x= 40°

Case 2:

When an angle measures 70°, and two equal angles measure x°.

Keeping the same property of triangle in mind, that is sum of interior angles of triangle is 180°.

70° + x° + x° = 180°

⇒  70° + 2 x° = 180°

⇒ 2 x° = 180° -  70°

⇒ 2 x° = 110°

Dividing both sides by 2, we get

x= 55°