Question

Two sides of a triangle are 12 and 18 cm. Complete the inequality to show the possible lengths of the third side.

Answer 1

Let a = 12 and b = 18 be the two given sides

Let c be the unknown third side

Due a modified form of the triangle inequality theorem, we know that,

b-a < c < b+a

18-12 < c < 18+12

6 < c < 30 which is the final answer

This says c is between 6 and 30, but cannot equal either endpoint.