Find the perimeter of a train of 100 equilateral triangles if the triangles are joined side to side. Each side is one inch long. Write an equation to determine the perimeter of the triangle train.

102

Step-by-step explanation:

Each triangle will have a perimeter of 3. When joined, the outside triangles will have 2 sides showing, or 2 inches. The middle 98 will only have one free side, or one inch. This means that 98*1 + 2*2 = 102