Boats and Streams Practice Questions

5 questions per page • Detailed step-by-step solutions

Question 1
Easy
Meera covers 20 km upstream in 600 minutes and she also covers 60 km downstream in 5 hours. Then find the rate of current of the river.
A 2.5 km/h
B 8 km/h
C 3 km/h
D 5 km/h
Correct Answer: D

Explanation:

Upstream speed = 20 / (600/60) = 20 / 10 = 2 km/h. Downstream speed = 60 / 5 = 12 km/h. Rate of current = (12 - 2) / 2 = 5 km/h.
Question 2
Medium
The ratio of the time taken by a boat to go a certain distance upstream and return downstream halfway of the same distance is 18:5. If the speed of stream is 4 km/h what is the distance covered by the boat in 6 hours in downstream and 8 hours in upstream?
A 192 km
B 188 km
C 208 km
D 175 km
Correct Answer: B

Explanation:

Upstream distance D, downstream distance D/2. Time ratio: [D/(u - v)] / [(D/2)/(u + v)] = 18 / 5 => 2(u + v) / (u - v) = 18/5 => (u + v)/(u - v) = 9/5 => u / v = 14/4 = 7/2. Since v = 4 km/h, u = 14 km/h. Downstream speed = 18 km/h, Upstream speed = 10 km/h. Total distance = 6 * 18 + 8 * 10 = 108 + 80 = 188 km.
Question 3
Easy
A boat is rowed downstream at 15.5 kmph and upstream at 8.5 kmph. The speed of the stream is :
A 3.5 kmph
B 4 kmph
C 7 kmph
D 4.5 kmph
Correct Answer: A

Explanation:

Speed of stream = (Downstream speed - Upstream speed) / 2 = (15.5 - 8.5) / 2 = 7 / 2 = 3.5 kmph.
Question 4
Easy
Ratio of time taken by a sailor to cover some distance upstream and downstream is 4 : 1. If speed of stream is 4.5 km/hr. Then find out speed of boat?
A 8.5 km/hr
B 9.5 km/hr
C 7.5 km/hr
D 8 km/hr
Correct Answer: C

Explanation:

Time Up : Down = 4 : 1 => Speed Down : Up = 4 : 1 => u / v = (4 + 1)/(4 - 1) = 5/3. Since v = 4.5 km/hr, boat speed u = (5/3) * 4.5 = 7.5 km/hr.
Question 5
Medium
The speed of a boat downstream is five times the speed of the stream. If the boat can travel 120 km in 5 hours while in upstream, then find the time taken by the boat to travel 480 km downstream and 180 km upstream.
A 19.5 hours
B 16.8 hours
C 12.75 hours
D 18.5 hours
Correct Answer: A

Explanation:

Let stream be x. Downstream = 5x => Still = 4x, Upstream = 3x. Upstream speed = 120 / 5 = 24 km/hr => 3x = 24 => x = 8 km/hr. Upstream = 24 km/hr, downstream = 40 km/hr. Total time = (480 / 40) + (180 / 24) = 12 + 7.5 = 19.5 hours.