Quantitative Aptitude: Boats and Streams Questions Set 8

  1. The still of boat in skill water is 7.5 km/h. If the speed of stream is 2.5 km/h, then find the time taken to go a distance of 15km and come back to starting point.
    4.5
    3
    4
    5
    3.5
    Option A
    Speed of boat = 7.5km/h
    speed of stream =2.5km/h
    downstream speed of boat = 7.5+2.5 =10km/h.
    Upstream speed of boat =7.5-2.5 =5km/h.
    Time required =15/10+15/5 =1.5+3 =4.5 hours.

     

  2. If the speed of boat in upstream and in downstream 10km/h and 20km/h respectively. Find the total distance covered by boat in still water in 6 hours .
    80km.
    90km.
    80km.
    85km.
    50km.
    Option B
    Upstream speed of boat= 10km/h.
    downstream speed of boat =20km/h.
    speed of boat in still water =20+10/2 =15 km/h.
    Total distance covered by boat =15*6 =90 km.

     

  3. The ratio of speed of boat in skill water and the current speed is 5:1 distance covered by boat in downstream speed and upstream speed is 120km. each find the speed of boat in skill water if total time taken boat in both downstream and upstream speed ids 10 hours.
    25
    28
    30
    40
    60
    Option A
    Let the speed of boat in skill water= 5x
    current speed =x
    downstream speed of boat =5x+x =6x
    upstream speed of boat =5x-x =4x
    120/6x+120/4x= 10
    20/x+30/x =10
    x=5
    speed of boat in still water =5*5 =25 km/hr

     

  4. A boat along the current takes 3 hours to cover a certain distance and against the current in takes 9 hours to cover the same distance . If speed of boat in still water is 4km/h, then find the speed the current.
    2
    3
    1
    1.5
    2.5
    Option A
    speed of boat in skill water =4km/h.
    Let current speed =x
    downstream speed =(4+x) km/h
    upstream speed =(4-x) km/h
    Let distance covered by boat =D km.
    ATQ,
    D/4+x =3
    D =12+3x……….(1)
    D /4-x =9
    D =36-9x…………(2)
    12+3x=36-9x
    12x =24
    x=2
    speed of current =2 km/h.

     

  5. A man’s speed with the current is 20 km/h and the speed of the current is 5km/h. Then find how much time will take by man to cover 90km in against the current.
    8
    6
    5
    9
    4
    Option D
    downstream speed of boat =20
    speed of current =5
    speed of boat =20-5 =15
    upstream speed of boat =15-5 =10
    Time required =90/10 =9 hour.

     

  6. Time taken by boat to cover 200 km in upstream is 10 hours more than the time taken by boat to cover 200 km in downstream. Total time taken by boat to cover 80 km in upstream is 8 hours. Find speed of boat in still water.
    15
    20
    25
    24
    10
    Option A
    let speed of boat and current be x km/hr and y km/hr respectively
    upstream speed of boat=80/8=10 km/hr
    downstream =x+y
    ATQ, 200/10-200/x+y=10
    20-200/x+y=10
    x+y=20
    downstream speed of boat=20 km/hr
    speed of boat in still water=20+10/2=15km/h

     

  7. The upstream speed of a boat is 20% less than the downstream speed. Find speed of boat in still water if it covers 100 km in downstream and 60 km in upstream in total 7 hours.
    25
    22.5
    24
    25.5
    28
    Option B
    let the downstream speed=5x
    upstream speed=4x
    ATQ, 100/5x+60/4x=7
    20/x+15/x=7
    x=5
    downstream speed=5*5=25
    upstream speed=4x=4*5=20
    boat speed=(25+20)/2=22.5 km/hr

     

  8. The speed of boat in still water is 18 km/hr and current speed is 6 km/hr. If time taken by boat to cover certain distance both downstream and upstream is 12 hours. Find the distance.
    100
    90
    75
    96
    84
    Option D
    speed of boat in still water=18
    speed of current=6
    downstream speed of boat=18+6=24
    upstream speed of boat=18-6=12
    let distance be D km
    D/24+D/12=12
    D=96 km

     

  9. The sum of the speed of a boat in still water and the current is 20 km/hr. The boat takes 8 hours to cover 96 km upstream. Find the difference between the speed of boat in still water and speed of current.
    14
    18
    16
    12
    10
    Option D
    let speed of boat in still water=x
    current speed=20-x
    upstream speed=96/8=12 km/hr
    x-(20-x)=12
    2x-20=12
    x=16 km/hr
    speed of boat in still water=16 km/hr
    current speed=20-16=4 km/hr
    difference=16-4=12 km/hr

     

  10. A boat takes 20 hours to cover 400 km in upstream and 12 hours to cover 480 km in downstream. Speed of boat in still water is how much percent more than speed of stream ?
    100%
    80%
    120%
    60%
    200%
    Option E
    upstream speed of boat=400/20=20 km/hr
    downstream speed of boat=480/12=40 km/hr
    speed of boat in still water=40+20/2=30 km/hr
    speed of current=40-20/2=10 km/hr
    percentage=30-10/10*100=200%

     

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