Probus wrote:

A man travels from City A to City B at 60 miles/hr, and returns to city A at 40 miles/hr. If the entire journey took 10 hrs in all then what is the distance between City A and City B?

(A)120

(B)240

(C)272

(D)280

(E)288

Total distance covered=AB+BA=2*AB

Total time taken=10 hours

Average speed=Total distance/Total time

So, Total distance=2*AB=Average speed*10

Question stem:- AB=?

Average speed=\(\frac{2v_{1}*v_{2}}{v_{1}+v_{2}}\)

Note:- Applicable when the distance covered at two speeds is same (here distance AB covered at 60 mph and distance BA covered at 40 mph, AB=BA)

So, average speed=\(\frac{2*60*40}{60+40}\)=48 mph

We have, 2*AB=48*10

Or, AB=240 miles

Ans. (B)

_________________

Regards,

PKN

Rise above the storm, you will find the sunshine