A man can row a distance of 5 km in 60 min with the help of the tide. The direction of the tide reverses with the same speed. Now he travels a further 20 km in 10 hours. How much time he would have saved if the direction of tide has not changed?
(a) 5 hrs (b) 4 hrs (c) 12 hrs (d)

• ans is 6 hrs
  5km in 1hr , so 20 km in 4 hr
  but he took 10 hr. he would have saved 10-4=6 hr
• 10 years agoHelpfull: Yes(21) No(0)
• dist=speed*time
  5=(u+v)*1hr
  20=(u-v)*10
  by slving u=7/2
  v=3/2
  therfore
  20=(u+v)*t
  20=(3/2 + 7/2)*t
  t=4hr
  time saved=6 hr
• 10 years agoHelpfull: Yes(4) No(0)
• Ans:6 hours
• 10 years agoHelpfull: Yes(1) No(0)
• for 1 hour he can travel 5km. if he travel in the same speed in 5 hours he reach 25km. so he can save 5 hrs
  ans is (a)5 hrs
• 10 years agoHelpfull: Yes(0) No(18)
• 6 hours, using downstream speed in both cases
• 9 years agoHelpfull: Yes(0) No(0)
• answer:
  
  given : he complete 5 km in 1 hour(60 min)
  but due to some reason his speed decreases to 20 km in 10 hours
  but with orignally speed ie 5 km/hr he would have completed this in 4 hour
  ie 20 km = 4 hour
  
  thus time required
  10hour - 4 hour = 6 hour
• 4 years agoHelpfull: Yes(0) No(0)