Question

#5 In *triangle* ABC, AB = 9 and BC = 15. What is the range the possible lengths for CA?
Why?

Answer 1

CA must be in the range [15 - 9, 15 + 9] = [6, 24]
For the line segments to form a triangle the length of CA cannot be less the the difference between the other sides or greater than their sum.
At either extreme the three points A, B and C will be co-linear thus forming a triangle with area of zero