Distance truck travels, Dt = 120 mi.
Distance car travels, Dc = 180 mi.
Rate of car = Rc
Rate of truck, Rt = Rc - 20
Time, T, is the same for both, so
T = D / R, therefore,
Dt / Rt = Dc / Rc
120 / (Rc - 20) = 180 / Rc
120Rc = 180(Rc - 20)
120Rc = 180Rc - 3600
120Rc - 180Rc = - 3600
- 60Rc = - 3600
Rc = - 3600 / - 60
Rc = 60
Rt = 60 - 20
Rt = 40
The truck is travelling an average of 40 mph and the car is travelling an average of 60 mph.
Distance truck travels, Dt = 120 mi.
Distance car travels, Dc = 180 mi.
Rate of car = Rc
Rate of truck, Rt = Rc - 20
Time, T, is the same for both, so
T = D / R, therefore,
Dt / Rt = Dc / Rc
120 / (Rc - 20) = 180 / Rc
120Rc = 180(Rc - 20)
120Rc = 180Rc - 3600
120Rc - 180Rc = - 3600
- 60Rc = - 3600
Rc = - 3600 / - 60
Rc = 60
Rt = 60 - 20
Rt = 40
The truck is travelling an average of 40 mph and the car is travelling an average of 60 mph.