Apatio floor is shaped like a rectangle with a width of w cm and a length of 21 ft. find an expression that represents the area of the floor.

The area of a rectangle is length x width.

Note that
1 in = 2.54 cm
1 cm = 1/2.54 = 0.3937 in 
1 cm = 0.3937/12 = 0.032808 ft
w cm = w*0.032808 = 0.032808w ft

Therefore the area of the floor is
(21 ft)*(21 cm)
= (21 ft x 0.032808w ft)
= 0.689w ft²

  0.689w ft²  (nearest hundredth)