(Teaser) The lengths of all sides of a triangle are integers when measured in decimeters. One of the sides has length of 1 dm and another of 3 dm. Find the perimeter of the triangle.

You are not going to be able to find a numerical value of this triangle because you do not know the type of triangle or the other side length. You can represent the perimeter using algebra though.

To find the perimeter you add the lengths of all 3 sides.

To show this as an algebraic expression, you would put 1 dm + 3 dm + x.

This will simplify to x + 4 dm, where x is the length of the missing side (in decimeter).