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Four couples have to cross a river by small boat. At a time only 4 person can travel...

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Four couples have to cross a river by small boat. At a time only 4 person can travel and it takes 15 min to cross river from one bank to another. Find minimum time to cross the river by them?

posted May 10, 2015 by Salil Agrawal

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3 Answers

+1 vote

one side of river ;;;;;;;;;;;;;;;;;;;;;;;;;;;;; other side of river ,,,,,,, total time

   8 persons ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;  0 persons   ,,,,,,,,,,,,,,,,,  t=0

    4  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;   4   ,,,,,,,,,,,,,,,,,,  15 min
    5  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;   3   ,,,,,,,,,,,,,,,,,,   30 
    1  ';;;;;;;;;;;;;;;;;;;;;;;;;;;;;;   7  ,,,,,,,,,,,,,,,,,,  45
    2   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;    6  ,,,,,,,,,,,,,,,,,,,  60
    0   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;     8  ,,,,,,,,,,,,,,,,,,  75 min

Hence total time is 75 min

answer May 11, 2015 by Ankit Kamboj
+1 vote

75 Minutes
2 couples (4 persons) ---> 15 Minutes
1 couple return ------------> 15 Minutes
2 couples (4 persons) ---> 15 Minutes
1 couple return ------------> 15 Minutes
2 couples (4 persons) ---> 15 Minutes

Total --------------------------> 75 Minutes

answer Sep 2, 2017 by Thillairajan
0 votes

minimum time will be thirty minutes

answer May 11, 2015 by Ben Gichuhi
There is only one boat so 30 mins can't be the answer.



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