The force
F
(in pounds) needed on a wrench handle to loosen a certain bolt varies inversely with the length
L
(in inches) of the handle. A force of 45 pounds is needed when the handle is 7 inches long. If a person needs 20 pounds of force to loosen the bolt, estimate the length of the wrench handle.
F = k/L so FL is constant. You want L such that
20L = 45*7