📢 Too many exams? Don’t know which one suits you best? Book Your Free Expert 👉 call Now!
  • google app store apple app store
    • ✖

      Question

      A boat can go 15 km upstream and 21 km downstream in 2

      hours. If the speed of the stream is 3 km/h, then the time taken (in hours) by the boat to go 21 km upstream and 15 km downstream is:
      A 2(4/35) Correct Answer Incorrect Answer
      B 3 Correct Answer Incorrect Answer
      C 3(/1/4) Correct Answer Incorrect Answer
      D 2(1/2) Correct Answer Incorrect Answer

      Solution

      Let the speed of boat in still water =B

      Let the speed of stream in still water =S

      Speed of boat in downstream =B+S

      Speed of boat in upstream =B-S

      B+S=21/2=10.5km/h

      B-S=15/2=7.5km/h

      Solving after –

      B=9km/h and S=1.5km/h

      ATQ-

      S =1.5 =3km/h

      B=9=18 km/h

      Now total taken time =

      (21/B-S) +(15/B+S)

      = (21/15) +(15/21)

      =74/35

      =2(4/35) hours

      Practice Next
      More Boats and streams Questions

      Relevant for Exams:

      ask-question