# Boat and Stream

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 =

Rate upstream =

Now, speed of the stream =

Hence option [B] is the right answer.

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 =

Hence option [C] is the right answer.

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 =

=7.5 kmph

Speed Of Current = 10-7.5 = 2.5 kmph

Hence option [D] is the right answer.

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 =

Hence option [A] is the right answer.

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 =

Hence option [D] is the right answer.

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 =

Let the speed of the current be x kmph

∴ 36 – x = 32

Speed of motor boat downstream = 36 + 4 = 40 kmph

∴ Time taken to cover 56 km at 40 kmph =

or 1 hours 24 minutes.

Hence option [B] is the right answer.

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.

…….(1)

…………(2)

On adding, 2x = 14 kmph = 7 kmph

Hence option [C] is the right answer.

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 =

Speed of current =

Hence option [D] is the right answer.

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 =

Time taken in swimming 60 km upstream =

From, given options, boy can swim 60km downstream in 4 hrs.

So option [B] is the right answer.

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]

[D]

**12 hours**

Rate downstream = 5 kmph

Rate upstream = 1 kmph

∴ Required time =

Hence option [A] is the right answer.