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Quiz: Boats and Streams

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Number of Questions: 40

Question: 26 -

A steamer moves with a speed of 4.5 km/h in still water to a certain upstream point and comes back to the starting point in a river which flows at 1.5 km/h. The average speed of steamer for the total journey is

Options:

  1. 10 km/h 

  2. 6 km/h 

  3. 12 km/h 

  4. 4 km/h 

    5. Answer:

    4 km/h 
    Solution:

    Speed of streamer = 4.5 km/hrSpeed of water = 1.5 km/hr

    Downstream speed = 4.5+1.5 = 6 km/hr

    Upstream speed = 4.5 -1.5 = 3 km/hr

    Average Speed = (6 X 3) / 4.5 = 4km/hr

Question: 27 -

Equal distance is covered by a boat in upstream and in downstream in total 5 hours. Sum of speed of a boat in upstream and downstream is 40 km/hr. Speed of boat in still water is 600% more than the speed of stream. Find theapproximate distance covered by boat in downstream (in km).

Options:

  1. 45

  2. 55

  3. 60

  4. 50

    5. Answer:

    50
    Solution:

    let speed of boat= X, speed of stream= Y
    Upstream speed= X-Y
    Downstream speed= X+Y
    Sum of upstream & downstream= (X-Y) +(X+Y)= 2X
    So, 2X= 40
    X= 20 km/hr
    Speed of boat : speed of stream= 600+100 :100= 7:1
    So speed of Stream= 20/7 km/hr
    ATQ, D/( X-Y) + D/( X+Y) = 5
    D/(120/7) + D/(160/7)= 5
    D= 480×5/49= 48.97 km= 50 Km(approx)

Question: 28 -

The ratio of the speed of a boat downstream and speed of the stream is 9:1. If the speed of the current is 3 km per hr, find the distance travelled by the boat upstream in 5 hours.

Options:

  1. 100 km 

  2. 98 km 

  3. 105 km 

  4. 109 km 

    5. Answer:

    105 km 
    Solution:

    Let the speed of boat in still water is ‘x’ km/hr & that of stream is ‘y’ km/hr.
    Then, ATQ
    (x+y)/y = 9/1 9y = x + y
    x = 8y
    y = 3 km/hr
    So, x = 24 km/hr
    Upstream speed = 24-3 = 21 km/hr
    Hence, distance travelled upstream in 5 hours = 21*5 = 105 km.

Question: 29 -

A boatman can row 3 km against the stream in 20 minutes and return in 18 minutes. Find the rate of current ?

Options:

  1. 1/3 kmph

  2.  2/3 kmph 

  3. 1/2 kmph 

  4.  1/4 kmph 

    5. Answer:

    1/2 kmph 
    Solution:

    Speed in upstream = Distance / Time = 3 x 60/20 = 9 km/hr.

    Speed in downstream = 3 x 60/18 = 10 km/hr

    Rate of current = (10-9)/2 = 1/2 km/hr.

Question: 30 -

Find the speed of stream if a boat covers 36 km in downstream in 6 hours which is 3 hours less in covering the same distance in upstream?

Options:

  1. 0.5 kmph 

  2. 0.75 kmph 

  3. 1.5 kmph 

  4. 1 kmph 

    5. Answer:

    1 kmph 
    Solution:

    Speed of the boat upstream = 36/9 = 4 kmph

    Speed of the boat in downstream = 36/6 = 6 kmph

    Speed of stream = 6-4/2 = 1 kmph