Answer: 20
The old perimeter is 4 and 4*5 = 20 is the new perimeter. We simply multiply the old perimeter by the scale factor. The units stay the same.
A more detailed break down would be that each piece of the shape gets stretched by the same factor, so each piece is 5 times larger than the original. If we had a square with side lengths 1, then the new side lengths would be 5. The old perimeter is 1+1+1+1 = 4 while the new perimeter is 5+5+5+5 = 20, which is five times larger than the old perimeter.
