A regular hexagon can be divided into six equilateral triangles. If the perimeter of one of the triangles is 21 inches, what is the perimeter, in inches, of the regular hexagon?
I know that a regular hexagon has six sides of equal length, so if I can find the length of one side, I can multiply it by six to get the perimeter of the hexagon. The problem tells me that the perimeter of one of the equilateral triangles is 21 inches, which means that each side of the triangle is 21/3 = 7 inches. This also means that each side of the hexagon is 7 inches, since the triangles are congruent and share a side with the hexagon. Therefore, the perimeter of the hexagon is 7 x 6 = 42 inches. 