The bathtub has dimensions 5 ft by 3 ft by 18 inches.
Note that 18 inches = 18/12 = 1.5 ft.
The volume of the bathtub is
V = 5*3*1.5 = 22.5 ft³
The bathtub is three-fourths (0.75) full of water. Therefore the volume of water is
0.75*22.5 = 16.875 ft³
The water is lost at the rate of 1 ft³/min.
If it takes x minutes to empty the bathtub, then
(1 ft³/min)*(x min) = (16.875 ft³)
x = 16.875 min
Answer: 16.875 minutes
