question_answer

A boat takes 19 hours to travel downstream from point A. to point B and coming back to a point C midway between A and B. If the speed of the stream is 4 km/hr and the speed of the boat in still water is 14 km/hr, what is the distance between A and B.?

A)  2001 km                      

B)  180 km

C)         160 km            

D)         220 km

E)         210 km

Correct Answer: B

Solution :

Let the total distance be D km According to the question, \[\frac{D}{14+4}+\frac{\frac{D}{2}}{14-4}=19\] Or \[\frac{D}{18}+\frac{D}{20}=19\] or\[\frac{10D+9D}{180}=19\] \[\therefore 19D=19\times 180\] \[\therefore D=180km\]