# A motorboat whose speed is 9 km/hr in still water, goes 15 km downstream and comes back in a total time of 3 hours 45 minutes. Find the speed of the stream.

Let the speed of stream be x km/h

Speed of boat is 9km/hr

Speed downstream = (9 + x)km/h

Speed upstream = (9 – x)km/h

Distance covered downstream = Distance covered upstream = 15km

Total time taken = 3 hours 45 minutes

taking LCM

81 – x2 = 72 cross multiplying

x2 = 81 – 72

x2 = 9 taking square root

x = 3 or – 3 (rejecting negative value)

Hence the speed of stream is 3 km/hr

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Related Videos
Quiz | Knowing the Nature of Roots44 mins
Take a Dip Into Quadratic graphs32 mins
Foundation | Practice Important Questions for Foundation54 mins
Nature of Roots of Quadratic Equations51 mins
Getting Familiar with Nature of Roots of Quadratic Equations51 mins
Quadratic Equation: Previous Year NTSE Questions32 mins
Champ Quiz | Quadratic Equation33 mins
Balance the Chemical Equations49 mins
Understand The Concept of Quadratic Equation45 mins
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation
view all courses