Question

Two sides of a triangle are 9 cm and 12 cm long. What is the range of possible lengths for the third side? Enter your answer in the boxes below.

Answer 1

I don't know the range, but a possible length is 15.

Answer 2

Possible length range of third side is between 3<x<21.

Explanation:

Sum of two sides of triangle cannot be equal or less than third side. Therefore, one side length of a triangle must be between subtract and sum of other two sides. Than, range of third side is:

`(12-9)<x<(12+9)\\3<x<21`