running a race

Question

April has 2 hours to for a race. She trains by running the full race then walking back.If she runs at 8mph and walks at 2mph how long will it take walk back

Answer 1

Let distance of race be D miles and let the time to run that distance be t hours

 

D = 8 t  ... running      Also D = 2 (2-t)  ... walking back, in 2 hours minus whatever running time was used.

 

So D = 8t = 2 (2 - t)

 

8t = 4 - 2t

 

10t = 4   so t = 2/5 of an hour (running).

 

Therefore it takes 1 & 3/5 hour to walk back, i.e. 1 hour and36 minutes.