Exercise :: Boats and Streams  General Questions
 Boats and Streams  Important Formulas
 Boats and Streams  General Questions
 Boats and Streams  Data Sufficiency 1
 Boats and Streams  Data Sufficiency 2
1.  A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream. 

Answer: Option C Explanation: Speed downstream = (13 + 4) km/hr = 17 km/hr.

2.  A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is: 

Answer: Option C Explanation: Man's rate in still water = (15  2.5) km/hr = 12.5 km/hr. Man's rate against the current = (12.5  2.5) km/hr = 10 km/hr. 
3.  A boat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively? 

Answer: Option C Explanation: Let the man's rate upstream be x kmph and that downstream be y kmph. Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs.
= 8 : 3. 
4.  A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is: 

Answer: Option B Explanation: Let the speed of the stream be x km/hr. Then, Speed downstream = (15 + x) km/hr, Speed upstream = (15  x) km/hr.
9x^{2} = 225 x^{2} = 25 x = 5 km/hr. Video Explanation: https://youtu.be/lMFnNB3YQOo 
5.  In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is: 

Answer: Option C Explanation: 