Question

a triangle has two sides of length 18 and 3. what is the largest possible whole-number length for the third side?

Answer 1

20

Explanation:

Triangle inequality says that the third side can only be 18-3...15, that is bigger than 15.

And 18+3... 21, that is smaller than 21.

If the third side is 21, the 18 and the 3 will just lay right on top of the 21 and not make a triangle. So it has to be 20 in order to be a whole number.