laurie can bike to work in 3/4 hour.when she takes the bus, the trip takes 1/4 hour. if the bus travels 20 mph faster than laurie rides her bike, how many miles is it to her workplace?
T(bike)= 3/4hour= 0.75hour
T(bus)1/4hour=0.25 hour
R(bus)=R(bike)+20
Since D = R*T, then we have the equation
T(bus)*(R(bike)+20)=T(bike)*R(bike)
0.25*R(bike)+ 5 =0.75*R(bike)
Thus, R(bike)=10mph
R(bus)= 10+20= 30mph
D = 10*0.75= 7.5 miles
or D = 30*0.25= 7.5 mies