Crossing the River...
Logic
Level
2
Four people need to cross a dark river at night.
- They have only one torch and can't cross the river without a torch.
- They can't all cross the river at the same time.
- Only two people can cross the river at one specific time.
- Speed of each person crossing the river is different.
- Cross time for the 4 people is 1 minute , 2 minutes , 7 minutes , and 10 minutes .
What is the shortest time needed for all four of them to cross the river?
19
23
21
17
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Answer
= ceiling[1,2] + 1 + ceiling[10,7] + 2 + ceiling[1,2]
= 2 + 1 + 10 + 2 + 2
= 17 minutes