# Boat and Stream

Quantitative Aptitude Questions and Answers section on “Boat and Stream” with solution and explanation for competitive examinations such as CAT, MBA, SSC, Bank PO, Bank Clerical and other examinations.
1.

A man rows a boat 18 kilometers in 4 hours downstream and returns upstream in 12 hours. The speed of the (in km/hr) stream is :
[A]1 km/hr
[B]1.5 km/hr
[C]1.75 km/hr
[D]2 km/hr

1.5 km/hr
Rate downstream = $\frac{18}{4}=\frac{9}{2} km/hr$
Rate upstream = $\frac{18}{12}=\frac{3}{2} km/hr$
Now, speed of the stream = $\frac{Rate Downstream - Rate Upstream }{2}$
$=>\frac{\frac{9}{2}-\frac{3}{2}}{2}=\frac{6}{4}=\frac{3}{2}$
$=>1.5 km/hr$
Hence option [B] is the right answer.

2.

A boatman rows 1 km in 5 minutes, along the stream and 6 km in 1 hour against the stream. The speed of the strean is :
[A]12 km/hr
[B]10 km/hr
[C]3 km/hr
[D]6 km/hr

3 km/hr
Speed of current = $\frac{Rate Downstream - Rate Upstream }{2}$
$=>\frac{1}{2}\left ( 12-6 \right )$
$=>\frac{1}{2}\times 6=3 km/hr$
Hence option [C] is the right answer.

3.

The speed of a boat in still water is 10 km/hr. It covers (upstream) a distance of 45 km in 6 hours. The speed (in km/hr) of the stream is :
[A]3.5 kmph
[B]4 kmph
[C]4 kmph
[D]2.5 kmph

2.5 kmph
Upstream speed of boat = $\frac{Distance}{Time}=\frac{45}{6}=\frac{15}{2}$
=7.5 kmph
Speed Of Current = 10-7.5 = 2.5 kmph
Hence option [D] is the right answer.

4.

A man rows 40 km upstream in 8 hours and a distance of 36 km downstream in 6 hours. Then speed of stream is :
[A]0.5 km/hr
[B]3 km/hr
[C]1.5 km/hr
[D]1 km/hr

0.5 km/hr
Speed of stream = $\frac{1}{2}\left ( \frac{36}{6}-\frac{40}{8} \right )$
$=>\frac{1}{2}(1)=\frac{1}{2}=0.5 kmph$
Hence option [A] is the right answer.

5.

If a boat goes 100 km downstream in 10 hours and 75 km upstream in 15 hours, then the speed of the stream is :
[A]3.5 km/hr
[B]2 km/hr
[C]3 km/hr
[D]2.5 km/hr

2.5 km/hr
Rate downstream = 10 kmph
Rate upstream = 5 kmph
∴ Speed of current = $\frac{1}{2}\left ( 10-5 \right )kmph$
$=>2.5km/hr$
Hence option [D] is the right answer.

6.

A motorboat in still water traveles at a speed of 36 kmph. It goes 56 km upstream in 1 hour 45 minutes. The time taken by it to cover the same distance down the stream will be :
[A]2 Hours 21 Minutes
[B]1 Hours 24 Minutes
[C]2 Hours 25 Minutes
[D]3 Hours

1 Hours 24 Minutes
Speed of the motorboat upstream =
$\frac{56 km}{1\frac{3}{4}hours} = \frac{56\times 4}{7} = 32 kmph$
Let the speed of the current be x kmph
∴ 36 – x = 32
$=> x = 36 - 32 = 4 kmph$
Speed of motor boat downstream = 36 + 4 = 40 kmph
∴ Time taken to cover 56 km at 40 kmph = $\frac{56}{40} = \frac{7}{5}hours$
or 1 hours 24 minutes.
Hence option [B] is the right answer.

7.

A boat running downstream covers a distance of 20 km in 2 hrs while it covers the same distance upstream in 5 hrs. Then speed of the both in still water is
[A]10 km/hr
[B]8 km/hr
[C]7 km/hr
[D]9 km/hr

7 km/hr
Let the speed of boat in still water be x kmph and that of stream be y kmph.
$\therefore \frac{20}{x+y} = 2$
$=> x+y = 10$ …….(1)
$\frac{20}{x-y} = 5$
$=> x-y = 4$…………(2)
On adding, 2x = 14 kmph = 7 kmph
Hence option [C] is the right answer.

8.

A boat travels 24 km upstream in 6 hours and 20 km downstream in 4 hours. Then the speed of boat in still water and the speed of water current are respectively
[A]5 km/hr and 2 km/hr
[B]4 km/hr and 2 km/hr
[C]4 km/hr and 3 km/hr
[D]4.5 km/hr and 0.5 km/hr

4.5 km/hr and 0.5 km/hr
Rate upstream = 4 kmph
Rate downstream = 5 kmph
∴ Speed of boat in still water = $\frac{1}{2}(4+5)$
$=> \frac{9}{2} = 4.5 kmph$
Speed of current = $\frac{1}{2}(5-4)$
$=> \frac{1}{2} = 0.5 kmph$
Hence option [D] is the right answer.

9.

A boy can swim in still water at a speed of 10 km/hr. If the speed of the current would have been 5kmph, then the boy could swim 60 km
[A]upstream in 6 hours
[B]downstream in 4 hours
[C]downstream in 12 hours
[D]upstream in 4 hours

downstream in 4 hours
Rate downstream = 10 + 5 = 15 kmph
Rate upstream = 10 – 5 = 5 kmph
Time taken in swimming 60 km downstream = $\frac{60}{15} = 4hours$
Time taken in swimming 60 km upstream = $\frac{60}{5} = 12hours$
From, given options, boy can swim 60km downstream in 4 hrs.
So option [B] is the right answer.

10.

A man can swim at 3km/hr in still water. If the velocity of the stream is 2km/hr, the time taken by him to swim to a place 10 km upstream and back is :
[A]12 hours
[B]10 hours
[C]$8\frac{1}{3}hours$
[D]$9\frac{1}{3}hours$

12 hours
Rate downstream = 5 kmph
Rate upstream = 1 kmph
∴ Required time = $\frac{10}{5}+\frac{10}{1} = 12 hours$
Hence option [A] is the right answer.