A person goes to his office at 1/3rd of the speed at which he returns from his office. If the avg speed during the whole trip is 12m/h. what is the speedof the person while he was going to his office?  Choose the correct choice from the following.
A) 8km/h
B) 9km/h
C) 10km/h
D) 12km/h
E) 14km/h
u = k , v= 3k   \inline \therefore \frac{2uv}{u+v}\: \: \Rightarrow \frac{2\times k\times 3k}{(k+3k)}=12   \inline \Rightarrow 1.5k = 12   \inline \Rightarrow k=8km/h   8km/h
<result>A</result>
A person goes to his office at 1/3rd of the speed at which he returns from his office. If the avg speed during the whole trip is 12m/h. what is the speedof the person while he was going to his office?