Home Aptitude Algebra Reasoning English PlacementPapers Technical GD's HRinterviewQuestions General BuyCRTBook

BoatsandStreams

AllthebasicconceptsofTimespeedandDistanceapplytothischapterBoatsandstreams.Wehavetoadjustthespeedsaccordingtothepointwhethertheboatismovingagainstthestreamorwiththestream.

Therearetwoparametersintheseproblems.

1.SpeedoftheStream(S):Thisisthespeedwithwhichtheriverflows.2.Speedoftheboatinstillwater(B):Iftheriverisstill,thisisthespeedatwhichtheboatwouldbemoving.

Theeffectivespeedofaboatinupstream=BSTheeffectivespeedofaboatindownstream=B+S

3.ThespeedoftheboatinstillwaterisgivenasB= ,andthespeedoftheStreamS= ,

wheredanduarethedownstreamandupstreamspeeds,respectively.

SolvedExamples

1.Agirlcanswim3km/hrinstillwater.Ifthevelocityofthestreambe2km/hrthetimetakenbyhertoswimtoaplace10kmupstreamandbackis:

a. hrs

NotFoundTherequestedURL/pagead/adswasnotfoundonthisserver.

1

1

search...

Submitaplacementquestion/Interviewexperience:Clickhere

Feedback/Suggestons:ClickHere

Follow 1k

Author:4.6kLike

b. hr

c.10hrsd.12hrsCorrectOption:DExplanation:Speedofupstream=(32)km/hr=1km/hrSpeedofdownstream(3+2)km/hr=5km/hr

Totaltimetaken= hrs=12hrs

2.Agirlcanrowthreequartersofakilometeragainstthestreamin minutesandreturnin minutes.The

speedofthegirlinstillwateris:a.2km/hrb.3km/hrc.4km/hrd.5km/hrCorrectOption:DExplanation:

Speedofupstream= = km/hr=4km/hr

Speedofdownstream= = km/hr=6km/hr

Speedinstillwater= km/hr=5km/hr

3.Agirlcanrow km/hrinstillwaterandshefindsthatittakesherthriceasmuchtimetorowupthanastorow

downthesamedistanceinriver.Thespeedofthecurrentis:

a. km/hr

b. km/hr

c. km/hr

g g

g g

NotFoundTherequestedURL/pagead/adswasnotfoundonthisserver.

Apache/2.2.16(Debian)Serveratgoogleads.g.doubleclick.netPort80

d. km/hr

CorrectOption:DExplanation:Letspeedofupstream=xkm/hrThen,speedofdownstream=3xkm/hr

Speedinstillwater= km/hr=2xkm/hr

Speedofthecurrent= km/hr=xkm/hr

orx= km/hr

4.Thecurrentofastreamrunsat1km/hr.Amotorboatgoes35km.upstreamandbackagaintothestartingpointin12hours.Thespeedofmotorboatinstillwateris:a.6km/hrb.7km/hrc.8.5km/hrd.8km/hrCorrectOption:AExplanation:Letthespeedinstillwaterbexkm/hr.

or35(2x)=12ororor12x(x6)+2(x6)=0or(x6)(12x+2)=0x=6km/hr

5.Amotorcovers24kmupstreamand36kmdownstreamin6hours,whileitcovers36kmupstreamand24km

downstreamin hours.Thevelocityofthestreamis:

a.1.5km/hr

4 4

4 4

4

4

4

4

4 4

4 4 4

b.1km/hrc.2km/hrd.2.5km/hrCorrectOption:CExplanation:Letthespeedofupstreambexkm/hrandthespeedofdownstreambeykm/hr.Then,

,whereu=1/x,v=1/y

And,

Addingtheseequations,weget oru+v=

Subtracting,weget oruv=

Solvingu+v= anduv= wegetu= andv=

x=8km/hrory=12km/hr

Velocityofcurrent= (128)km/hr=2km/hr

6.Thecurrentofstreamrunsattherateof4kmanhour.Aboatgoes6kmandbacktothestartingpointin2hours.Thespeedoftheboatinstillwateris:a.6km/hrb.7.5km/hrc.8km/hrd.6.8km/hrCorrectOption:CExplanation:Letthespeedinstillwaterbexkm/hr

Then,

1 2

4

5

1 2

4

5

1 2

1 2

4

4

or(x8)(x+2)=0.So,x=8km/hr

7.Amanrowstoaplace48kmdistantandbackin14hours.Hefindsthathecanrow4kmwiththestreaminthesametimeas3kmagainstthestream.Therateofthestreamis:a.0.5km/hrb.1km/hrc.3.5km/hrd.1.8km/hrCorrectOption:BExplanation:Supposehemoves4kmdownstreaminxhours

Then,speedofdownstream= km/hr

Speedofupstream= km/hr

Speedofdownstream=8km/hrSpeedofupstream=6km/hr

Rateofstream= km/hr=1km/hr

8.Aboatmovesupstreamattherateof1kmin10minutesanddownstreamattherateof1kmin6minutes.Thespeedofthecurrentis:a.1km/hrb.1.5km/hrc.2km/hrd.2.5km/hrCorrectOption:CExplanation:Speedofupstream=6km/hrSpeedofdownstream=10km/hr

4 4 4

4

4

4 4

4

4

4

Speedofthecurrent= km/hr=2km/hr

9.Agirlrowsupstream16kmanddownstream28km,taking5hourseachtime.Thevelocityofthecurrentis:a.2.4km/hrb.1.2km/hrc.3.6km/hrd.1.8km/hrCorrectOption:BExplanation:

Speedofdownstream= km/hr=5.6km/hr

Speedofupstream= km/hr=3.2km/hr

Velocityofcurrent= km/hr

=1.2km/hr

10.Speedofaboatinstandingwateris6km/hrandthespeedofthestreamis1.5km/hr.Amanrowstoaplaceatadistanceof22.5kmandcomesbacktothestartingpoint.Thetotaltimetakenbyhim,is:a.6hrs30minb.8hrs24minc.8hrsd.4hrs12minCorrectOption:CExplanation:Speedofupstream=(61.5)km/hr=4.5km/hrSpeedofdownstream==(6+1.5)km/hr=7.5km/hr

Totaltimetaken= hrs=8hrs.

11.Amancanrowat5km/hrinstillwaterandthevelocityofcurrentis1km/hr.Ittakeshim1hourtorowtoaplaceandback.Howfaristheplace?a.2.5kmb.2.4km

c.3kmd.3.6kmCorrectOption:BExplanation:Speedofdownstream=(5+1)km/hr=6km/hrSpeedofupstream=(51)km/hr=4km/hrLettherequireddistancebexkm.

Then,

orx=2.4km

12.AboattravelsupstreamfromQtoPanddownstreamfromPtoQin3hours.Ifthespeedoftheboatinstillwateris9km/hrandthespeedofthecurrentis3km/hr,thedistancebetweenPandQis:a.4kmb.6kmc.8kmd.12kmCorrectOption:DExplanation:Speedofdownstream=(9+3)km/hr=12km/hrSpeedofupstream=(93)km/hr=6km/hrLetthedistanceAB=xkm

Then,

2x+x=36\Rightarrowx=12$DistanceAB=12km.

13.Amotorgoes40kmupstreamin8hoursand36kmdownstreamin6hours.Thespeedoftheboatinstandingwateris:a.6.5km/hrb.6km/hrc.5.5km/hrd.5km/hrCorrectOption:C

4 4

4

4

4

4

Explanation:

Speedofupstream= km/hr=5km/hr

Speedofdownstream= km/hr=6km/hr

Speedofboatinstillwater

= km/hr=5.5km/hr

14.Ifaman'smovingratewiththecurrentis12km/hrandtherateofthecurrentis1.5km/hr,thenman'smovingrateagainstthestreamis:a.9km/hrb.6.75km/hrc.5.25km/hrd.7.5km/hrCorrectOption:AExplanation:Lettherateagainstthecurrentbexkm/hrThen,

km/hr

15.Ifamanrowsat5km/hrinstillwaterand3.5km/hragainstthecurrent,hisratealongthecurrentis:a.8.5km/hrb.6.5km/hrc.6km/hrd.4.25km/hrCorrectOption:BExplanation:Lettheratealongthecurrentbexkm/hr

Then, =6.5km/hr

16.Thespeedofaboatdownstreamis15km/hrandthespeedofthestreamis1.5km/hr.Thespeedoftheboatupstreamis:a.13.5km/hrb.16.5km/hr

4 4

4

4

4

c.12km/hrd.8.25km/hrCorrectOption:CExplanation:Letthespeedofboatinstillwaterbexkm/hrThen,x+1.5=15 x=13.5Speedofupstream=(13.51.5)km/hr=12km/hr

17.Thespeedofaboatinstillwateris2km/hr.Ifitsspeedupstreambe1km/hr.thenspeedofthestreamis:a.1.5km/hrb.3km/hrc.1km/hrd.NoneoftheseCorrectOption:CExplanation:Letthespeedofstreambexkm/hrThen,speedofupstream=(2x)km/hr2x=1 x=1km/hr

18.Amancanrowdownstreamat14km/hrupstreamat9km/hr.Man'srateinstillwaterisa.5km/hrb.23km/hrc.11.5km/hrd.NoneoftheseCorrectOption:CExplanation:

Man'srateinstillwater= km/hr=

11.5km/hr

19.Agirlcanrowwiththestreamat11km/hrandagainstthestreamat8km/hr.Thespeedofthestreamis:a.3km/hrb.9.5km/hr

c.1.5km/hrd.6km/hrCorrectOption:CExplanation:

Speedofstream= km/hr=1.5km/hr

20.Ifamanrowsattherateof5kmphinstillwaterandhisrateagainstthecurrentis3.5kmph,thentheman'sratealongwithcurrentis:a.4.25kmphb.6kmphc.6.5kmphd.8.5kmphCorrectOption:CExplanation:Lettheratealongthecurrentbexkmph

Then, =5orx=6.5KMPH.

AdditionalQuestions:

21.Amanrows27kmdownstreamand18kmupstreamtaking3hreachtime.Whatisthevelocityofthecurrent?

Ratedownstream= =9km/hr

Rateupstream= =6km/hr

Velocityofcurrent= (96)=1.5km/hr.

22.Amancanrowupstreamat7km/hranddownstreamat10km/hr.Findhisrateinstillwaterandtherateofthecurrent.

Rateinstillwater= =0.5(10+7)=8.5km/hr

Rateofcurrent= 0.5(107)=1.5km/hr

23.AmanrowsaboatfrompointAagainstcurrentfor10minutesandthencomebackwiththecurrentfornext

4

1

1

10minutesandreachestoapointB.IfdistancebetweenAandBis1km,findthespeedofthecurrent.Goingwithcurrentandagainstcurrentforthesametimemeansspeedoftheboatinstillwaterisneutralized.Speedofcurrentonlymovestheboat.

Boatismoved1kmbythecurrentin(10+10)minutes=20minute= hour.

Therefore,Speedofcurrent=1x3=3km/h.

24.Amancanrowaboatat6km/hinstillwaterandspeedofthecurrentis2km/h.Ifhetakes45minutestorowtheboattoaplaceandback.Findthedistancebetweenthetwoplaces.Speedoftheboatdownstream=6+2=8km/hSpedoftheboatupstream=62=4km/h

Therefore,Averagespeed= km/h

Timetaken=45minute= hour= hour

25.Amanrowsboattoaplacecovering72kmdistanceandbackin15hours.Hefindsthathecanrow3kmwiththestreaminthesametimeas2kmagainstthestream.Findthespeedofthestream.Speeddownstream:Speedupstream=3:2Therefore,Timetakentorowdownstream:Timetakentorowupstream=2:3But,totaltimetaken=15hours.

Therefore,Timetakentorowdownstream= x15hours=6hours

And,timetakentorowupstream=156=9hours

Therefore,Speeddownstream= =12km/h

And,speedupstream= =8km/h

Therefore,Speedofthestream= =2km/h

AlternativeMethod:Let,downstreamandupstreamspeedsare3km/hand2km/hrespectively.

Then,distancecoveredin15hours= =36km

But,actualdistancecovered=2x72km=144km(i.e.4times36km)Therefore,Speedsare4x3=and4x2,i.e.12and18km/h

Therefore,Speedofthestream= =2km/h

g g

g g

g

g g

1

0Like

NotFoundTherequestedURL/pagead/adswasnotfoundonthisserver.

Apache/2.2.16(Debian)Serveratgoogleads.g.doubleclick.netPort80

0Comments Campusgate Login1

Share SortbyNewest

Startthediscussion

Bethefirsttocomment.

Subscribe AddDisqustoyoursited Privacy

Recommend

Home