4 persons have to cross the bridge. Their speeds are 1, 2, 5, 10 min respectively. Only two persons can cross at a time and as it is night they have to carry torch (i.e. one have to return with the torch). What is the minimum time required for all of them to reach the other side? When two persons cross they go by the speed of slowest one

• 17 mins
  
  First of all we mark these persons as numbers 1,2,5,10.
  
  1 and 2 cross in 2 mins,
  2 comes back in 2 mins.
  5 and 10 cross in 10 mins.
  1 comes back in 1 min
  1 and 2 cross in 2 mins.
  total 2+2+10+1+2 = 17 mins
• 12 years agoHelpfull: Yes(5) No(5)