Quants Questions : Time and Distance Set 3 – Boats

Hello Aspirants. Welcome to Online Quantitative Aptitude Section in AffairsCloud.com. Here we are creating question sample in Time and Distance- Boats and streams with Explanation, which is common for all the IBPS,SBI,SSC and other competitive exams. We have included Some questions that are repeatedly asked in bank exams !!!

  1. If Nishu can swim downstream at 6kmph and upstream at 2kmph.What is his
    speed in still water ?
    A.5 km/hr
    B.4 km/hr
    C.8km/hr
    D.7km/hr
    Answer
    Answer- B
    Basic Formula:

    If the speed downloadstream is a km/ hr and the speed upstream is b km/ hr
    then Speed in still water is = ½ (a+b) km / hr [memory tool last 2 L cross and make +]            Explanation:
    Given : speed downstream a = 6 km ph
    Speed upstream b = 2kmph
    Speed in still water = ½ (a+b) kmph
    = ½ (6+2)
    = 8/2 = 4kmph
    speed in still water = 4kmph
  2. Ashok can row upstream at 8kmph and downstream at 12kmph.What is the
    speed of the stream ?
    A.6km/hr
    B.3km/h
    C.2 km/hr
    D.4km/hr
    Answer
    Answer -C 
    Basic Formula:
    If the speed downstream is a kmph and the speed upstream is b kmph
    then
    Speed of the stream = ½ (a-b) kmph
    Explanation:
    Speed downstream a = 12kmph
    Speed upstream b = 8 kmph
    Speed of the stream = ½ (a-b) = ½ (12-8)
    = 4/2 = 2 kmph
    speed of the stream = 2kmph
  3. A man rows 750m in 775 seconds against the stream and returns in 7
    1/2 minutes. What is rowing speed in still water ?
    A.4.7km/hr
    B. 4km/hr
    C.3.5km/hr
    D.6km/hr
    Answer
    Answer-A 
    Basic Formula:
    i) Speed in still water = ½ (a+b) kmph where ‘a’ is speed
    downstream and ‘b’ is speed upstream
    ii) a km / hr = a x 5/18 m /s
    iii) a m/sec = a x 18/5 km/hr
    Explanation:
    Speed upstream ‘b’ = 750m / 775 sec = 30/31 m/sec
    Speed downstream ‘a’ = 750 m/ (15/2)minutes [ 1min=60 sec] a = 750m/450 sec =5/3 m/sec
    speed in still water = ½ (a+b)
    = ½ (750/450 + 750/675 ) m /sec
    = ½ (750/450 + 750/675 ) x 18/5 km/hr
    = ½ (5/3 + 30/31) x 18/5 km/hr
    = 4.7 km/hr
  4. A man 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 the current ?
    A. 5km/hr
    B.3(1/2) km/hr
    C.4 (2/3) km/hr
    D.8 (3/2)km/hr
    Answer
    Answer- C
    Basic Formula:
    Speed of current = ½ (a-b) km/hr
    Explanation:
    Let man’s rate upstream be x km/hr. Then his rate downstream is 3 x km/hr
    Given:
    Speed in still water = 9 (1/3) = 28/3 km/hr
    i.e, ½ (a+b) = 28/3 km/hr
    ½ (x+3x) = 28/3
    2x = 28/3    x = 28/ 2 x 3 = 14/3 km/hr
    rate upstream b = 14/3 km/hr and
    rate downstream a = 14/3 x 3 = 14 km/hr
    speed of the current = ½ (a-b) = ½ (14 – 14/3)
    = ½ (42-14/3) = 28/6 = 4 (2/3) km/hr
  5. Sham can row a boat at 10kmph in still water. IF the speed of the
    stream is 6kmph, the time taken to row a distance of 80km down the stream
    is
    A.4 hours
    B.5hours
    C.3 hours
    D.2 hours
    Answer
    Answer- B
    Basic Formula:
    Speed of stream = ½ (a-b) km/hr
    Speed in still water = ½ (a+b) km/hr
    Explanation:
    Given:
    Speed in still water, ½ (a+b) = 10 km/hr
    a+b = 20 km/hr…………….(1)
    speed of the stream, ½ (a-b) = 6km/hr
    a-b = 12 km/hr …………….(2)
    (1)+(2 ) we get 2a = 32
    a = 16 km/hr
    speed downstream =distance traveled / time taken
    time taken = 80/16 = 5 hours
  6. A boat takes 4hours for traveling downstream from point P to point
    Q and coming back to point P upstream. If the velocity of the stream is 2km
    ph and the speed of the boat in still water is 4kmph, what is the distance
    between P and Q?
    A.9 km
    B.7 km
    C.5 km
    D.6km
    Answer
    Answer- D
    Basic Formula:
    Speed of stream = ½ (a-b) km/hr
    Speed of still water = ½ (a+b) km/hr
    Explanation:
    Time taken by boat to travel upstream and downstream = 4 hours
    Velocity of the stream, ½ (a-b) = 2km/hr
    a-b = 4km/hr ……………….( 1)
    velocity of the boat in still water = ½ (a+b) = 4km/hr
    a+b = 8 km/hr ………………(2)
    1 +2 we get a = 6 km/hr ,b = 2km/hr
    let the distance between A and B be x km
    x / 2 + x / 6 = 4
    3x + x / 6 = 4  4x = 24 so,x = 6
    distance between P and Q = 6km
  7. Speed of a boat in standing water is 9kmph and the speed of the
    stream is 1.5kmph. A man rows to a place at a distance of 10.5 km and
    comes back to the starting point. Find the total time taken by him.
    A.24 hours
    B.16 hours
    C.20 hours
    D.15 hours
    Answer
    Answer- A
    Basic Formula:
    i. speed = distance traveled / time taken
    ii. speed of the stream = ½ (a-b) km/hr
    iii. speed in still water = ½ (a+b) km/hr
    Explanation:
    Speed in still water= ½ (a+b) = 9km ph
    = a+b = 18 …………….1
    speed of the stream = ½ (a-b) = 1.5 kmph
    = a-b = 3 kmph…………2
    solving 1 and 2 gives a = 10.5km/hr ; b=7.5 kmphr
    Total time taken by him = 105/10.5 + 105/7.5 = 24 hours
  8. A man rows to a place 48km distant and back in 14 hours. He finds
    that he can row 4km with the stream in the same time as 3km against the
    stream. Find the rate of the stream.
    A.2 km/hr
    B.1 km/hr
    C.3 km/hr
    D.3.5km/hr
    Answer
    Answer- B
    Basic Formula:
    Speed of the stream = ½ (a-b) km / hr
    Speed = distance traveled / time taken
    Explanation:
    Suppose he moves 4km downstream in x hours
    Then, downstream a= 4 / x km/hr
    Speed upstream b = 3/ x km/hr
    48 / (4 /x) + 48 / (3/x) = 14
    12x + 16x = 14
    x = 1/2
    a=8 km/hr ,b = 6 km/hr
    rate of stream = ½ (8 – 6 )
    =  1 km/hr
  9. There is road besides a river. Two friends started from a place P, moved to a shopping mall
    situated at another place Q and then returned to P again. One of them moves on a cycle at
    a speed of 12 km/hr, while the other sails on a boat at a speed of 10 km/hr. If the river
    flows at the speed of 4 km/hr, which of the two friends will return to place P?
    A. Both
    B. Boater
    C. Cyclist
    D. None of these
    Answer
    Answer-C
    Explanation:
    The cyclist moves both ways at a speed of 12khr so average speed fo the
    cyclist – 12 km/hr
    boat sailor moves downstream at 10+4 = 14km/hr and upstream 10-
    4 = 6km/hr
    Average speed of the boat sailor = 2 x 14 x 6 / 14 +6 = 42/ 5 = 8.4km/hr
    The average speed of cyclist is greater .so,cyclist comes first and return to
    place P.
  10. A this usual rowing rate, Mohit can travel 12 miles downstream in a certain river in 6
    hours less than it takes him to travel the same distance upstream. But if he could double
    his usual rowing rate for his 24 miles round trip, the downstream 12 miles would then
    take only one hour less than the upstream 12 miles. What is the speed of the current in
    miles per hour?
    A.2.5m/hr
    B.4 m/hr
    C.8/3 m/hr
    D. 5/3m/hr
    Answer
    Answer-C
    Basic Formula:
    Speed of the stream = ½ (a-b) km/hr
    Explanation:
    Let the speed in still water be x m/hr
    Speed of stream be y m/hr
    Then, speed upstream = x-y m/hr and
    Speed downstream = x+y m/hr
    12/x-y – 12 / x+y = 6 so,6 (x^2 – y^2) = 24 y
    x^2 – y^2 = 4y
    x^2 = y^2 + 4y…………..1
    also
    12/ 2x-y – 12/2x +y = 1 4x^2 – y^2 = 24y
    x^2 = [24y + y^2] / 4 ……………….2
    16y + 4y^2 = 24y + y2 [put X^2 value from 1] 3y^2 = 8 y so, y = 8/3
    speed of the current = 8/3 m/hr = 2 (2/3) m/hr