A motorboat, whose speed in 15km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. the speed of the stream (in km/hr) is:
(a) 4 (b) 5 (c) 6 (d) 10 (e) none of these

• Total time take to travel up and down =9/2hrs ==>given,
  i,e===> 30/(15+x)+30/(15-x)=9/2hrs,
  By simplification
  =====>200=225-x^2
  =====>x^2=25
  =====>x=5km/hr
  SO ANS: 5km/hr.
• 9 years agoHelpfull: Yes(1) No(0)