Question

The length of two sides of an isosceles triangle are 9 cm and 20 cm. What is the perimeter of the triangle? Given reason.

Answer 1

Third side can be either 20 cm or 9 cm,because as it is an isoceles triangle two side length must be equal.
(0.5 marks)

Now, as we know that sum of two sides of a triangle must be greater than third side.So if we take third side as 9 cm, then 9cm + 9cm < 20cm .
(1 mark)

Hence, third side must be 20 cm.
(0.5 marks)

$\therefore$ Perimeter of the triangle = Sum of all sides = (9 + 20 + 20) cm
= 49 cm
(1 mark)