A Rickety Bridge Riddle
Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?
Hint:
17 mins.
The initial solution most people will think of is to use the fastest person as an usher to guide everyone across. How long would that take? 10 + 1 + 7 + 1 + 2 = 21 mins. Is that it? No. That would make this question too simple even as a warm up question.
Let's brainstorm a little further. To reduce the amount of time, we should find a way for 10 and 7 to go together. If they cross together, then we need one of them to come back to get the others. That would not be ideal. How do we get around that? Maybe we can have 1 waiting on the other side to bring the torch back. Ahaa, we are getting closer. The fastest way to get 1 across and be back is to use 2 to usher 1 across. So let's put all this together.
1 and 2 go cross
2 comes back
7 and 10 go across
1 comes back
1 and 2 go across (done)
Total time = 2 + 2 + 10 + 1 + 2 = 17 mins Did you answer this riddle correctly?
YES NO
The initial solution most people will think of is to use the fastest person as an usher to guide everyone across. How long would that take? 10 + 1 + 7 + 1 + 2 = 21 mins. Is that it? No. That would make this question too simple even as a warm up question.
Let's brainstorm a little further. To reduce the amount of time, we should find a way for 10 and 7 to go together. If they cross together, then we need one of them to come back to get the others. That would not be ideal. How do we get around that? Maybe we can have 1 waiting on the other side to bring the torch back. Ahaa, we are getting closer. The fastest way to get 1 across and be back is to use 2 to usher 1 across. So let's put all this together.
1 and 2 go cross
2 comes back
7 and 10 go across
1 comes back
1 and 2 go across (done)
Total time = 2 + 2 + 10 + 1 + 2 = 17 mins Did you answer this riddle correctly?
YES NO
Up And Down At The Same Time
Hint:
Time And Commitment Riddle
With time and commitment you will find this.
And learning to have it alleviates stress in your life.
What is it?
And learning to have it alleviates stress in your life.
What is it?
Hint:
In Times Of War Riddle
Hint:
Around You All The Time Riddle
Hint:
The Nurses Office Riddle
Hint:
Angry Mother Needle Riddle
Hint:
Turning 200 Times Riddle
Hint:
An Octopuses Fav Time Of The Year
Hint:
Died In Office
Hint:
Officer Bob Riddle
Hint:
Bugged Officer Riddle
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Time To Chill Riddle
Hint:
Meeting Your Fate
If you ever happen to see one of these etched
With your name, birth year and a future date
You might want to be worried that there is someone
Who knows when it is youll meet your fate
What is this?
With your name, birth year and a future date
You might want to be worried that there is someone
Who knows when it is youll meet your fate
What is this?
Hint:
Four Times To Infinity
Hint:
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