Find the dimensions of the rectangle with area 225 square inches that has minimum perimeter, and then find the minimum perimeter.

Question

Dimensions:

Minimum perimeter:

Answer 1

Just from experience, I would have bet that the answer was l=w=15, i.e. a square....so let's prove it

W=225/L

P=2L + 450/L

dP/dL = 2 - (450/L²)...set it equal to 0

2L² = 450

L=15