Let's start with the formula for the perimeter of a rectangle of length L and width W: P = 2W + 2L. We are told that this perimeter is 16. What is the length, L, of the rectangle?
Solving 16 = 2W + 2L for L:
2L = 16 - 2W, or L = 8 - W
Important: since L cannot be negative, W must be 8 or smaller, but not negative or zero.
Checks: If W=8, L = 8 - 8 = 0 This is reasonable.
If W is just barely greater than 0, L = 8 - 0+, or approx. 8. This is reasonable also.
Answer: 0<L<8
