Boat and Stream Aptitude Questions with Solutions:


Overview:


Questions and Answers Type:MCQ (Multiple Choice Questions).
Main Topic:Quantitative Aptitude.
Quantitative Aptitude Sub-topic:Time Speed and Distance Aptitude Questions and Answers.
Number of Questions:10 Questions with Solutions.

  1. If a man swims \(10 \ km\) upstream and \(12 \ km\) downstream, taking \(2 \ hours\) each time, then find the speed of stream?

    1. \(0.3 \ km/hr\)
    2. \(0.4 \ km/hr\)
    3. \(0.5 \ km/hr\)
    4. \(1.0 \ km/hr\)


Answer: (c) \(0.5 \ km/hr\)

Solution: Given, speed of upstream \((U_s) = \frac{10}{2} = 5 \ km/hr\)

speed of downstream \((D_s) = \frac{12}{2} = 6 \ km/hr\)

then speed of stream, $$ S_s = \frac{D_s - U_s}{2} $$ $$ = \frac{6 - 5}{2} = 0.5 \ km/hr $$

  1. If a girl can swim \(18 \ km\) upstream and \(26 \ km\) downstream, taking \(2 \ hours\) each time, then find speed of the girl in still water?

    1. \(10 \ km/hr\)
    2. \(11 \ km/hr\)
    3. \(12 \ km/hr\)
    4. \(15 \ km/hr\)


Answer: (b) \(11 \ km/hr\)

Solution: Given, speed of upstream \((U_s) = \frac{18}{2} = 9 \ km/hr\)

speed of downstream \((D_s) = \frac{26}{2} = 13 \ km/hr\)

then speed of the girl in still water, $$ B_s = \frac{D_s + U_s}{2} $$ $$ = \frac{9 + 13}{2} = 11 \ km/hr $$

  1. If a boat goes \(30 \ km\) upstream and \(45 \ km\) downstream, taking \(3 \ hours\) each time, then find the speed of stream and speed of the boat in still water?

    1. \(S_s = 2.5 \ km/hr\), \(B_s = 12.5 \ km/hr\)
    2. \(S_s = 3.5 \ km/hr\), \(B_s = 13.5 \ km/hr\)
    3. \(S_s = 2.5 \ km/hr\), \(B_s = 15.5 \ km/hr\)
    4. \(S_s = 5.5 \ km/hr\), \(B_s = 12.5 \ km/hr\)


Answer: (a) \(S_s = 2.5 \ km/hr\), \(B_s = 12.5 \ km/hr\)

Solution: Given, speed of upstream \((U_s) = \frac{30}{3} = 10 \ km/hr\)

speed of downstream \((D_s) = \frac{45}{3} = 15 \ km/hr\)then speed of stream, $$ S_s = \frac{D_s - U_s}{2} $$ $$ = \frac{15 - 10}{2} = 2.5 \ km/hr $$ then speed of the boat in still water, $$ B_s = \frac{D_s + U_s}{2} $$ $$ = \frac{15 + 10}{2} = 12.5 \ km/hr $$

  1. A man swims from point A to B and takes \(2 \ hours\) for traveling upstream from point A to B and coming back from point B to A downstream. If the speed of stream is \(10 \ km/hr\) and speed of the man in still water is \(12 \ km/hr\), then find the distance between point A and B?

    1. \(2.58 \ km\)
    2. \(2.67 \ km\)
    3. \(3.67 \ km\)
    4. \(3.58 \ km\)


Answer: (c) \(3.67 \ km\)

Solution: Given, speed of stream \((S_s) = 10 \ km/hr\)

speed of the man in still water \((B_s) = 12 \ km/hr\), then

speed of upstream \((U_s) = B_s - S_s\) \(= 12 - 10 = 2 \ km/hr\)

speed of downstream \((D_s) = B_s + S_s\) \(= 12 + 10 = 22 \ km/hr\)

Let the distance between point A and B = \(x \ km\), then $$ \frac{x}{22} + \frac{x}{2} = 2 $$ $$ \frac{12 \ x}{22} = 2 $$ $$ 12 \ x = 44 $$ $$ x = \frac{44}{12} = 3.67 \ km $$ Hence the distance between the point A and B = \(3.67 \ km\)

  1. If a boat goes downstream with the speed of \(16 \ km/hr\) and upstream with the speed of \(14 \ km/hr\), then find the speed of the boat in still water?

    1. \(12 \ km/hr\)
    2. \(13 \ km/hr\)
    3. \(14 \ km/hr\)
    4. \(15 \ km/hr\)


Answer: (d) \(15 \ km/hr\)

Solution: Given, speed of downstream \((D_s) = 16 \ km/hr\)

speed of upstream \((U_s) = 14 \ km/hr\)

then speed of the boat in still water, $$ B_s = \frac{U_s + D_s}{2} $$ $$ = \frac{14 + 16}{2} $$ $$ = \frac{30}{2} = 15 \ km/hr $$

  1. If a boat goes downstream at the speed of \(9 \ km/hr\) and speed of stream is \(4 \ km/hr\), then find the speed of boat in still water?

    1. \(5 \ km/hr\)
    2. \(6 \ km/hr\)
    3. \(4 \ km/hr\)
    4. \(2 \ km/hr\)


Answer: (a) \(5 \ km/hr\)

Solution: Given, speed of downstream \((D_s) = 9 \ km/hr\)

speed of stream \((S_s) = 4 \ km/hr\)

then speed of the boat in still water, $$ B_s = D_s - S_s $$ $$ = 9 - 4 = 5 \ km/hr $$

  1. A girl can swim \(28 \ km\) downstream, taking \(4 \ hours\). If speed of stream is \(3 \ km/hr\), then find the speed of upstream?

    1. \(1 \ km/hr\)
    2. \(2 \ km/hr\)
    3. \(3 \ km/hr\)
    4. \(5 \ km/hr\)


Answer: (a) \(1 \ km/hr\)

Solution: Given, speed of downstream \((D_s) = \frac{28}{4} = 7 \ km/hr\)

speed of stream \((S_s) = 3 \ km/hr\), then $$ S_s = \frac{D_s - U_s}{2} $$ $$ 3 = \frac{7 - U_s}{2} $$ $$ 6 = 7 - U_s $$ $$ U_s = 1 \ km/hr $$

  1. A boat goes \(16 \ km\) upstream, taking \(2 \ hours\). If speed of stream is \(2 \ km/hr\), then find the speed of downstream?

    1. \(15 \ km/hr\)
    2. \(13 \ km/hr\)
    3. \(12 \ km/hr\)
    4. \(10 \ km/hr\)


Answer: (c) \(12 \ km/hr\)

Solution: Given, speed of upstream \((U_s) = \frac{16}{2} = 8 \ km/hr\)

speed of stream \((S_s) = 2 \ km/hr\), then $$ S_s = \frac{D_s - U_s}{2} $$ $$ 2 = \frac{D_s - 8}{2} $$ $$ 4 = D_s - 8 $$ $$ D_s = 12 \ km/hr $$

  1. A boat goes downstream with the speed of \(25 \ km/hr\). If the speed of the boat in still water is \(15 \ km/hr\), then find the speed of upstream?

    1. \(2 \ km/hr\)
    2. \(3 \ km/hr\)
    3. \(4 \ km/hr\)
    4. \(5 \ km/hr\)


Answer: (d) \(5 \ km/hr\)

Solution: Given, speed of downstream \((D_s) = 25 \ km/hr\)

speed of boat in still water \((B_s) = 15 \ km/hr\), then $$ B_s = \frac{D_s + U_s}{2} $$ $$ 15 = \frac{25 + U_s}{2} $$ $$ 30 = 25 + U_s $$ $$ U_s = 5 \ km/hr $$

  1. A boat goes upstream with the speed of \(22 \ km/hr\). If the speed of the boat in still water is \(8 \ km/hr\), then find the speed of downstream?

    1. \(12 \ km/hr\)
    2. \(13 \ km/hr\)
    3. \(14 \ km/hr\)
    4. \(15 \ km/hr\)


Answer: (c) \(14 \ km/hr\)

Solution: Given, speed of upstream \((U_s) = 22 \ km/hr\)

speed of the boat in still water \((B_s) = 18 \ km/hr\), then $$ B_s = \frac{D_s + U_s}{2} $$ $$ 18 = \frac{D_s + 22}{2} $$ $$ 36 = D_s + 22 $$ $$ D_s = 14 \ km/hr $$