Question

Irina rode her bike to work at an average speed of 16 miles per hour. It started to rain, so she got a ride home along the same route in her coworker’s car at an average speed of 27 miles per hour. If Irina’s ride home in the car took 24 minuets (0.4 of an hour), how many hours was her bike ride to work, to the nearest tenth of an hour?

Answer 1

0.7 of an hour. :)

Bike to work: D=16*T

Ride home: D = 27*.4 =10.8

Solve for T

10.8 = 16*T

T = 10.8/16

0.7 of an hour.

Answer 2

Here, the distance traveled is not given, but Irina's bike-riding speed is:  it is 16 mph.

Let the distance traveled be d.  Then d = (27 mph)(0.4 hr) = 10.8 miles.

By bicycle, distance = rate times time.  Here, 10.8 miles = (16 mph)(time), and so

               10.8 mi

time = --------------- = 0.675 hour (40.5 minutes).

            16 mph