Quantitative Aptitude: Boats and Streams Questions Set 7

1. A boat running downstream covers a distance of 36 km in 4 hrs and for covering the same distance upstream it takes 9 hrs. What is the speed of the stream?
   2.5 km/hr
   3 km/hr
   4.5 km/hr
   5 km/hr
   None of these
   Option A
   Downstream speed = 36/4 = 9 km/hr
   Upstream speed = 36/9 = 4 km/hr
   So, speed of stream = 1/2*(9-4)=2.5 km/hr
   
    



2. It takes 5 times as long to row a distance against the stream as to row the same distance in favor of stream. What is the ratio of the speed of the boat in still water to that of stream?
   7:5
   3:2
   2:5
   1:6
   None of these
   Option B
   B = [t1u + t1d] / [t1u – t1d] * R
   So,B =[5x + x] / [5x- x] * R
   So B/R = 6/4 = 3:2
   
    



3. Rakesh rows to a place 40 km distant and back in total of 18 hours. He finds that he can row 5 km with the stream in same time as 4 km against the stream. What is the speed of boat in still water?
   3.0 km/hr
   4.5 km/hr
   4.5 km/hr
   6 km/hr
   5 km/hr
   Option C
   Suppose he moves 5 km downstream in t hours
   Then, downstream speed a= 5/t km/hr
   Speed upstream speed b = 4/t km/hr
   40 / (5 /t) + 40 / (4/t) = 18
   8t + 10t = 18
   t = 1
   a = 5 km/hr, b = 4 km/hr
   speed of boat = ½ (5 + 4 ) =4.5 km/hr
   
    



4. If Neelaksh can swim downstream at 6 kmph and upstream at 2 kmph.What is his speed in still water ?
   9 km/hr
   7 km/hr
   5 km/hr
   4 km/hr
   None of these
   Option D
   Speed downstream a = 6 kmph
   Speed upstream b = 2kmph
   Speed in still water = ½ (a+b) kmph
   = ½ (6+2) = 8/2 = 4kmph
   
    



5. Akansha can row upstream at 8 kmph and downstream at 12 kmph.What is the speed of the stream ?
   5 km/hr
   7 km/hr
   8 km/hr
   5 km/hr
   2 km/hr
   Option E
   Speed of the stream = ½ (x-y) = ½ (12-8)
   = 4/2 = 2 kmph
   
   
    



6. Ramesh rows to a place 48 km distant and back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against stream. Find the rate of the stream?
   1 km/hr
   3 km/hr
   5 km/hr
   6 km/hr
   None of these
   Option A
   Speed of the stream = ½ (x-y) km/ hr
   Speed = distance traveled / time taken
   
    



7. Shivani can row a boat at 10 kmph in still water. If the speed of the stream is 6 kmph, the time taken to row a distance of 80 km down the stream is ?
   is
   5 hours
   2 hours
   3 hours
   4 hours
   None of these
   Option A
   Speed in still water, ½ (a+b) = 10 km/hr
   a+b = 20 km/hr…………….(1)
   speed of the stream, ½ (x-y) = 6km/hr
   x-y = 12 km/hr …………….(2)
   (1)+(2 ) we get 2x = 32
   x= 16 km/hr
   speed downstream =distance traveled / time taken
   time taken = 80/16 = 5 hours
   
    



8. Srikant can row 9 (1/3) kmph in still water and finds that it takes him thrice as much time to row up than as to row down the same distance in the river. What is speed of current ?
   4 (2/3) km/hr
   7 (2/3) km/hr
   5 (1/3) km/hr
   7 km/hr
   None of these
   Option A
   Speed in still water = 9 (1/3) = 28/3 km/hr
   i.e, ½ (x+y) = 28/3 km/hr
   =½ (x+3x) = 28/3
   2x = 28/3 = x = 28/ 2 x 3 = 14/3 km/hr
   rate upstream = 14/3 km/hr and
   rate downstream = 14/3 x 3 = 14 km/hr
   speed of the current = ½ (x-x) = ½ (14 – 14/3)
   = ½ (42-14/3) = 28/6 = 4 (2/3) km/hr
   
    



9. Vikas goes downstream 60 km and upstream 20 km, taking 4 hrs each. What is the speed of current?
   8 km/hr
   5 km/hr
   10 km/hr
   2 km/hr
   4 km/hr
   Option B
   Downstream speed = 60/4 = 15 km/hr
   Upstream speed = 20/4 = 5 km/hr
   Speed of stream = (15-5)/2 = 5 km/hr
   
    



10. Akash rows downstream 28 km and upstream 16 km, taking 5 hrs each time. What is the velocity of current?
    1.2 km/hr
    1.8 km/hr
    2 km/hr
    1.5 km/hr
    None of these
    Option A