What is the greatest perimeter of a rectangle with an area of 39 sq. ft.?

To find the answer you do 39×4. You multiply by 4 because there are 4 sides.

This will be the biggest number.

Rectangle A: 
-- Length = 20-ft, Width = 10-ft. 
-- Area = 200 square ft 
-- Perimeter = 60-ft 

Rectangle B: 
-- Length = 16-ft, Width = 12.5-ft 
-- Area = 200 square ft 
-- Perimeter = 57-ft 

Rectangle C: 
-- Length = 40-ft, Width = 5-ft 
-- Area = 200 square ft 
-- Perimeter = 90-ft 

Rectangle D: 
-- Length = 50-ft, Width = 4-ft 
-- Area = 200 square ft 
-- Perimeter = 108-ft 

Rectangle E: 
-- Length = 100-ft, Width = 2-ft 
-- Area = 200 square ft 
-- Perimeter = 204-ft 

Rectangle F: 
-- Length = 800-ft, Width = 3 inches 
-- Area = 200 square ft 
-- Perimeter = 1600-ft 6-in

Just divide the x axis (the top) by 2 or multiply the y axis (the bottom) by 2