# Homework Help: Running and Walking

1. Jan 29, 2005

### hieule

Tim and Rick both can run at speed v_r and walk at speed v_w, with v_r greater than v_w. They set off together on a journey of distance D. Rick walks half of the distance and runs the other half. Tim walks half of the time and runs the other half.

the time it takes tim to cover the distance is:
t_R =((D/2)/v_w)+((D/2)/v_r)

the time it takes rick to cover the distance is:
t_T =2*D/(v_w+v_r)

In terms of given quantities, by what amount of time, Delta t, does Tim beat Rick?
Express the difference in time, Delta t in terms of v_r, v_w, and D.

this is an easy problem because all i need to do is take the Rick's time minus Tim's time right? i've done it and my answer is incorrect.

Last edited: Jan 29, 2005
2. Jan 29, 2005

### Parth Dave

You would take tim's time minus rick's time since tim takes less time. After that it is just algebra. All you have to do is simplify it.

3. Jan 29, 2005

### hieule

that's my problem. i couldn't simplify it correctly. i simplified it to be

(2D(VwVr)-D/2(Vr+Vw)(Vw+Vr))/((Vw+Vr)(VwVr))
but this is not the answer

4. Oct 5, 2011