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
Soldiers On The River
A detachment of soldiers must cross a river. The bridge is broken, the river is deep. What to do? Suddenly the officer-in-charge spots two boys playing in a rowboat by the shore. The boat is so tiny, however, that it can only hold 2 boys or 1 soldier. Still - all the soldiers succeed in crossing the river in the boat. How?
Hint:
First the boys cross the river. One stays ashore while the other brings the boat to the soldiers. A soldier takes the boat back across and the boy that stayed before brings the boat back and picks up the other boy. The boat takes the two boys back and one remains while the other boy returns the boat to the soldiers. This is repeated until all of the soldiers are on the opposite side of the river. Did you answer this riddle correctly?
YES NO
YES NO
The Game Of Bridge Riddle
Hint:
Everyone Needs My Help Riddle
I dig out tiny caves, and store gold and silver in them. I also build bridges of silver and make crowns of gold. They are the smallest you could imagine. Sooner or later everybody needs my help, yet many people are afraid to let me help them.
Who am I?
Who am I?
Hint:
Outrunning A Train Riddle
Walking home one day, you take a short cut along the train tracks. The tracks cross a narrow bridge over a deep gorge. At the point you are 3/8 of the way across the bridge, you hear the train whistle somewhere behind you. You charge across the bridge, and jump off the track as the train is about to run you down. As it happens, if you had gone the other way, you would have reached safety just before being run over as well. If you can run ten miles per hour, how fast is the train moving?
Hint:
The train is moving at 40 miles per hour. Imagine that a friend is walking with you. When the train whistle blows, you head away from the train, he heads toward it. When he reaches safety, you will be 6/8 (or 3/4)of the way across the bridge, and the train will have just reached the bridge. For the train to cross 4/4 of the bridge in the time you cross the remaining 1/4, the train must be moving four times your speed. Did you answer this riddle correctly?
YES NO
YES NO
Soldiers Across A River
A detachment of soldiers must cross a river. The bridge is broken, the river is deep. What to do?
Suddenly the officer in charge spots two boys playing in a row boat by the shore.
The boat is so tiny however, that is could only hold two boys or one soldier.
Still all the soldiers make it across the river in the boat. How?
Suddenly the officer in charge spots two boys playing in a row boat by the shore.
The boat is so tiny however, that is could only hold two boys or one soldier.
Still all the soldiers make it across the river in the boat. How?
Hint:
First the boys cross the river and 1 boy comes back and gets a soldier and keeps going back until all the soldiers have made it across safely. Did you answer this riddle correctly?
YES NO
YES NO
A Goat, A Wolf, And A Head Of Cabbage
A man has a goat, a wolf, and a head of cabbage. He comes to a river that has no bridge, but a small boat to cross the river. The boat can hold only one of the three things he has. If he takes over the wolf first, the goat will eat the cabbage. If he take over the cabbage first, the wolf will eat the goat.
How does he solve the problem?
How does he solve the problem?
Hint:
First, he takes over the goat. Then, he takes over the cabbage, but takes the goat back. Then, he takes over the wolf. Finally, he takes over the goat again. Did you answer this riddle correctly?
YES NO
YES NO
Not A Single Person Riddle
While walking across a bridge I saw a boat full of people. Yet on the boat there wasn't a single person. Why?
Hint:
I Sit On A Bridge
Hint:
Sunglasses. They sit on the bridge of your nose, you look through it but other people wonder what I hide. Did you answer this riddle correctly?
YES NO
YES NO
Building With Silver And Gold
Hint:
Brownie Currency
You're going to a friends house and want to give them some brownies. On the way to their house you cross 5 bridges. At each bridge you must pay a toll of half of your brownies to the owner. But they are all very nice and give you back a brownie from what you give them.
How many brownies must you start with to give your friend 2 brownies?
How many brownies must you start with to give your friend 2 brownies?
Hint:
Just 2.
Each time you give the owner of a bridge half of your brownies (1 brownie) they give you one back as well. Did you answer this riddle correctly?
YES NO
Each time you give the owner of a bridge half of your brownies (1 brownie) they give you one back as well. Did you answer this riddle correctly?
YES NO
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