Four persons can cross a bridge in 3,7,13,17 minutes. Only two can cross at a time. Find the minimum time taken by the four to cross the bridge.

• ans:20
  At minute 0, persons C (13) and D (17) begin crossing. At minute 13, person C is finished and person B (7) starts. At minute 17, D is finished and A (3) can start. At minute 20, both A and B finish.
  
• 12 years agoHelpfull: Yes(44) No(0)
• 7+3+17+7+7 =41 mins
• 13 years agoHelpfull: Yes(2) No(23)
• First (17) and (7) going ----->(7) will reach first der in 7 **min-----> remain 10 min left for (17)
  Now in that left 10 min (13) will join with (17) -------->As (17) already completed 7 min walk in 10** min he will reach--------> remain 3min for (13)
  Now (3) will join with (13) left time is 3 min so that both reached in 3** min.
  so totall min to reach is 7+10+3=20
• 8 years agoHelpfull: Yes(2) No(0)