Quantitative Aptitude-More exercise questions

Boats and Streams-Exercise Questions

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1.   A person can row 750 metres  against the stream in 11 ¼ minutes and returns in 7 ½ minutes. The
      speed of the person in in still water is :

      a) 2 km/hr b)3 km/hr         c)4km/hr          d) 5 km/hr

 

2.   If a man rows at the rate of 6 kmph in still water and his rate aginst the current is 4.5 kmph, then
      the man’s rate along the current is

      a) 6 kmph  b)7.5 kmph     c) 6.5kmph      d) 8 kmph       

 

3.   A boat moves upstream at the rate of 1 km in 20 minutes and down stream 1 km in 12 minutes. The
     speed  of the current is :

     a) 1 kmph b)2 kmph         c)3 kmph         d)2.5 kmph

 

4.   A man can row  a boat at 10 kmph in still water and  the speed of the stream is 8 kmph. What is the
     time taken to row a distance of 90 km down the stream ?

     a) 8hrs                   b)5 hrs                        c) 15 hrs          d) 20 hrs

 

5.   If athul  rows 16 km upstream and 24 km down steam  taking 4 hours each, then the speed of the
      stream

          a) 1kmph  2)kmph            3)1.5 kmph      12 kmph

 

Answer & Explanations

 

1. The speed in upstream = .75 * (4/45 )*60 = 4 kmph

    The speed in downstream = .75 *(2/15) *60 = 6 kmph

    Speed in still water = ½(4+6) = 5 kmph

2. Let the rate along the current be x kmph

   Then, ½ (x+ 4.5) = 6  :. x = 7.5

3. Rate upstream = (1/20 *60)  = 3 kmph

    Rate dowm stream = 1/12 * 60 = 5 kmph

    Rate of the current = ½ (5-3) = 1 kmph

4. Speed in down stream = 10 +8 = 18

   Time taken to cover 90 km  down stream = 90/18 = 5 hrs. 

5. Speed upstream = 16/4 = 4 kmph

   Speed down stream = 24/4 = 6 kmph

   Speed of stream = ½ (6-4) = 1 kmph

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