Four people need to cross a dark river at night.They have only one torch and the river is too risky to cross without the tourch. if all people cross simultanoesly then torch light wont be sufficient.Speed of each person of crossing the river is different.cross time for each person is 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the river ?

• 17 minutes
  1st and 2nd go together - 2 min then 2nd comes back- 2min
  then 3rd and 4th go together - 10 min and 1st comes back - 1min
  then finally 1st and 2nd go together - 2 min
  total time= 2+2+10+1+2=17 min
• 9 years agoHelpfull: Yes(8) No(1)
• Go :- 1 & 2 = 2 Min
  R: 1 = 1 Min
  Go: 1 & 7= 7 Min
  R: 1 = 1 Min
  Go: 1 & 10 = 10 Min
  Total: 2+1+7+1+10= 21 Min
• 5 years agoHelpfull: Yes(0) No(1)
• first 1 and 2 will go cross
  2 will come back
  7 and 10 go cross
  1 will come back
  1 and 2 will go cross
  then
  2+2+10+1+2=17mins
• 4 years agoHelpfull: Yes(0) No(0)