Boats and Streams


  1. A man can row 6 km/h in still water. If the speed of the current is 2 km/h, it takes 3 h more in upstream than in the downstream for the same distance. The distance is ?









  1. View Hint View Answer Discuss in Forum

    Let total distance be x km.
    According to the question,
    x/(6 + 2) + 3 = x/6 - 2

    Correct Option: B

    Let total distance be x km.
    According to the question,
    x/(6 + 2) + 3 = x/6 - 2
    ⇒ x/8 + 3 = x/4
    ⇒ x/4 - x/8 = 3
    ⇒ 2x - x/8 = 3
    ∴ x = 8 x 3 = 24 km


  1. Pawan can row 24 km/h in still water. When the river is running at 4.8 km/h, it takes him 1 h to row to a place and to come back. How far is the place ?









  1. View Hint View Answer Discuss in Forum

    Pawan's speed downstream = 24 + 4.8 = 28.8 km/h
    Pawan's speed upstream = 24 - 4.8 = 19.2 km/h
    Let the required distance be x.

    According to the question.
    x/28.8 + x/19.2 = 1

    Correct Option: A

    Pawan's speed downstream = 24 + 4.8 = 28.8 km/h
    Pawan's speed upstream = 24 - 4.8 = 19.2 km/h
    Let the required distance be x.

    According to the question.
    x/28.8 + x/19.2 = 1
    ⇒ (19.2x + 28.8x) / 552.96 = 1
    ⇒ 19.2x + 28.8x = 552.96
    ⇒ 48x = 552.96
    ∴ x = 552.96/48 = 11.52 km



  1. Sameer can row a certain distance downstream in 24 h and can come back covering the same distance in 36 h. If the stream flows at the rate of 12 km/h, find the speed of Sameer in still water ?









  1. View Hint View Answer Discuss in Forum

    Let the speed of Sameer in still water be x km/h
    Sameer's speed downstream = (x + 12) km/h
    Sameer's speed upstream = (x - 12) km/h
    According to the question, 24(x + 12) = 36(x - 12)

    Correct Option: D

    Let the speed of Sameer in still water be x km/h
    Sameer's speed downstream = (x + 12) km/h
    Sameer's speed upstream = (x - 12) km/h
    According to the question, 24(x + 12) = 36(x - 12)
    ⇒ 2x + 24 = 3x - 36
    ⇒ x = 36 + 24 = 60 km/h


  1. A sailor sails a distance of 48 km along the flow of a river in 8 h. If it takes 12 h to return the same distance, then the speed of the flow of the river is ?









  1. View Hint View Answer Discuss in Forum

    Let speed of the flow of water be x km/h and rate of sailing of sailor be y km/h.
    Downstream speed (x + y) = 48/8
    ⇒ x + y = 6 ....(i)
    and upstream speed x - y = 4 ...(ii)

    Correct Option: B

    Let speed of the flow of water be x km/h and rate of sailing of sailor be y km/h.
    Downstream speed (x + y) = 48/8
    ⇒ x + y = 6 ....(i)
    and upstream speed x - y = 4 ...(ii)
    On solving Eqs. (i) and (ii), we get
    y = 1 km/h



  1. speed of a boat in standing water is 7 km/hr and the speed of the stream is 1.5 km/hr. A distance of 7.7 km. going upstream is covered in ?









  1. View Hint View Answer Discuss in Forum

    Upstream speed = 7 - 1.5 = 5.5 km/hr
    ⇒ 5.5 x T = 7.7

    Correct Option: C

    Upstream speed = 7 - 1.5 = 5.5 km/hr
    ⇒ 5.5 x T = 7.7
    ∴ T = 77.7 / 5.5 = 1hr. 24 minutes