DI on Boat and Stream

A chunk of Questions is asked from Data Interpretation in the Quantitative Aptitude Section of banking exams. In todays exam scenario most of the DI 's are asked from a perticular topic like time and work,time and distance,boat and stream, partnership etc.   In this study note we will discuss DI (Data Interpretation)  based on Boat and Stream which are frequently asked in various competitive exams.

Direction: study the following graph and answer the given question.

The line graph shows the speed of stream.

Question 1:  The speed of the boat on Monday in still water is 125% of the speed of the boat on Wednesday in still water. If the speed of the boat on Wednesday is 16 km/hr, then what will be the ratio of the time taken by the boat on Monday to travel upstream to the time taken by the boat on Wednesday to travel downstream?

a) 29:67                                b) 55:83                c) 38:53                 d) 27:82                e) None of these

Solution:

Given that speed of the boat in still water on Wednesday= 16kmph

Also speed of the boat in still water on Monday= 16*125/100=20 kmph

We know that speed= Distance/time

Also upstream speed= x-y and downstream speed= x + y

Then upstream time of the boat on Monday= (20*440) / (100*(20-4)) =5.5

Downstream time of the boat on Wednesday= (15*600) / (100*(16+2)) =5

Required ratio= 5.5:5=11:10

Question 2:  If the ratio of the speed of boat on Tuesday in still water to the speed of boat Thursday in still water is 4:5, then what will be the approximate average time taken by boat on Thursday to travel upstream and downstream together if the speed of boat on Tuesday in still water is 20 km/hr?

a)10 hr                                  b)6 hr                    c) 2 hr                    d) 5 hr                   e) 8hr

Solution:

Let the speed of boat on Tuesday in still water be 4x and speed of boat on Thursday in still water be 5x.

Then given that 4x= 20

x= 5 km/hr

Then the speed of boat Thursday in still water=5*5=25km/hr

Now, time taken by the boat to travel upstream on Thursday= (24*440)/ (100*22.8)  = 4.5 hours (approximately)
And time taken by the boat to travel downstream on Thursday=(25*600)/(100*27.2)  =5.5 hours (approximately)

Required average= (4.5+5.5)/2= 5 hours

Question 3:  Time taken by the boat to cover the upstream distance on Monday is same as time taken by the boat to cover the downstream distance on Tuesday. If total speed of the boat in still water on Monday and Tuesday is 25 km/h, then find the ratio of the speed of still water on Monday and Tuesday?

a) 1:4                                     b)2:5                      c)3:2                      d)3:5                      e) 5:3

Solution:

Let x be the speed of the boat in still water on Monday and y be the speed of the boat in still water on Tuesday.

We know that Time=Distance/Speed

Also given that, x + y=25

Then y= 25-x

Now, 88/(x-4) =120/(y+5)

88/(x-4) =120/ (25-x+5)

11/(x-4)=15/(30-x)

11(30-x) = 15(x-4)

330-11x   = 15x-60

390 = 26x

x= 15 km/hr

Then y= 10 km/hr

Required ratio=15:10=3:2

Question 4:  On Wednesday, the boat takes a total time 10 hr 30 minutes to cover both upstream and downstream distance. If the ratio of speed of boat in still water is going upstream and downstream if 4:3 then find the speed of boat in still water while going downstream?

a) 24km/h                           b) 18km/h           c) 17km/h            d)15km/h            e) 7km/h

Solution:

Let speed of boat in still water is going in upstream= 4x

And speed of boat in still water is going in downstream=3x

We know that, Time= Distance/speed

Then [132/(4x-2)]+90/(3x+2)]=10(1/2)

After solving we get x= 6 km/hr.

Then 3x= 18 km/hr

Question 5: The time taken by the boat on Friday to travel downstream is  1h more than the time taken by the boat to travel upstream on Thursday. Find the approximate total time taken by the boat in still water on Thursday to travel the distance equivalent  to the distance covered  by the boat on Thursday in downstream if the speed of the boat on Friday in still water is 3.5 km/h?

a) 24hrs 32mins                 b) 23hrs 20 mins               c) 36 hrs 24 mins               d)34 hrs 40 mins             e) 25 hrs 40 mis

Solution:

Given that, the speed of the boat in still water= 3.5 km/hr

Now, time taken by the boat on Friday to travel Downstream= (30*600)/(100*(3.5+2.5))

= 30 hours

Then time taken by the boat on Thursday to travel upstream= 30-1=29 hours

Upstream speed of the boat on Thursday= (24*440)/(100*29)= 3.64 km/hr

Then speed of the boat in still water on Thursday= 3.64+2.2=5.84 km/hr

And downstream speed of the boat on Thursday= 5.84+2.2= 8.04 km/hr

Thus time taken by the boat on Thursday in still water= (25*600)/(100*5.84)  = 25 hours 40 minutes (approximately)