A tractor trailer combination has a 24,500 Ib tractor and a 12,300 lb trailer. The combination is going down a muddy hill. The tractor has wide, soft tires that float on top of the mud, (rolling resistance = 80 lb/ton). The trailer has narrow, hard tires that sink deeply in the mud (rolling resistance combination to roll downhill at a constant speed without the application of any rim pull from the engine? Assume the combination is already moving. %3D 220 lb/ton). What percent of downhill grade is required for the %3!

A tractor trailer combination has a 24,500 Ib tractor and a 12,300 lb trailer. The combination is going down a muddy hill. The tractor has wide, soft tires that float on top of the mud, (rolling resistance = 80 lb/ton). The trailer has narrow, hard tires that sink deeply in the mud (rolling resistance combination to roll downhill at a constant speed without the application of any rim pull from the engine? Assume the combination is already moving. %3D 220 lb/ton). What percent of downhill grade is required for the %3!