Aman can row 1km upstream in 20 min and back to his starting point in 12 min.How long would he take to row 1km in still water?.

• If his speed is x mtr/min in still water and w mtr/minis speed of water, then
  x-w= 1000/20=50
  x+w= 1000/12= 250/3
  adding
  2x= 50 + 250/3= 400/3
  x=200/3 mtrs/min
  time taken to row 1 kms in still water = 1000/(200/3)= 15 mins.
  
• 11 years agoHelpfull: Yes(3) No(0)
• Ans 15 min.
  If Speed of Aman =a , Stream=s
  In upstream, Speed=a-s Given 1/(a-s) =1/3 or a-s=3 ---(i)
  In downstream Speed=a+s,Given 1/(a+s)=1/5 or a+s=5 ---(ii)
  Solving we have a=4 km/hr
  So time taken in still water for Aman to row= 1/4 Hr.= 15 minutes
  
• 11 years agoHelpfull: Yes(1) No(1)
• In all such upstream/downstream problems, as distance remain same, the time is HM
  of two times.
• 11 years agoHelpfull: Yes(1) No(1)
• Using the formula of harmonic mean 2ab/(a+b), the result would be
  2*20*12/32 = 15 min
  
• 11 years agoHelpfull: Yes(1) No(0)