Get them across the river

  • #1
DeathKnight
73
0
There are six people. They are: A king, A queen, A knight and his wife, A servent and his wife. There is one boat and they all want to cross the river. The problem is: the boat cannot take more than 2 people. Your job is to tell them a way so that they can all get across the river.
Rules:
1-Women are free to take other women with them on the boat.
2-Men cannot take any woman except their wives on the boat.
3-If a man finds two women alone he'll run away with them. For example, if the king finds his wife and some other woman alone. He'll run away with them. You must not allow such thing to happen.
I hope you understand the rules.
 

Answers and Replies

  • #2
GregA
210
0
might be wronge here but...

king picks up the queen and drops her off at the other side
king returns for the Knight who then drops off the king at the other side
Knight picks up his wife who then drops the knight off at the other side
Knight's wife returns for the servants wife (but remains in the boat so the servant can't run away with the girls)
servants wife drops off knights wife before finally picking up her husband
 
  • #3
DeathKnight
73
0
GregA said:
Knight's wife returns for the servants wife (but remains in the boat so the servant can't run away with the girls)
Since the servant has two girls, he'll run away with them. So that's a wrong answer.
 
  • #4
GregA
210
0
lemme try again :biggrin:

king drops off the queen and returns for knight
knight drops off king and returns for his wife
knight exchanges his wife for the king
king and knight both disembark, servant drops off his wife
now that all the three girls are together they can all get across
 
  • #5
DeathKnight
73
0
GregA said:
king and knight both disembark, servant drops off his wife.
The servant has now 3 girls :devil:. So he'll definitely run away with them.:biggrin:
This brain teaser does have an answer. But I won't reveal it just yet.
 
Last edited:
  • #6
NateTG
Science Advisor
Homework Helper
2,452
7
Let's call the couples AaBb and Cc.

So we have
AaBCc |
King takes queen across, and returns with the boat.
ABbCc|a
Two wives take boat across, and queen comes back.
AaBC|bc
Husbands take boat across, and the knight returns with his wife.
AaBb|Cc
King and knight take boat across (leaving the queen and the knights wife), and
the servant's wife takes boat back.
abc|ABC
The queen drops off the knights wife, on the other side, and returns
ac|ABbC
then the last two women cross.
 
  • #7
Rahmuss
222
0
DeathKnight said:
There are six people. They are: A king, A queen, A knight and his wife, A servent and his wife. There is one boat and they all want to cross the river. The problem is: the boat cannot take more than 2 people. Your job is to tell them a way so that they can all get across the river.
Rules:
1-Women are free to take other women with them on the boat.
2-Men cannot take any woman except their wives on the boat.
3-If a man finds two women alone he'll run away with them. For example, if the king finds his wife and some other woman alone. He'll run away with them. You must not allow such thing to happen.
I hope you understand the rules.

I'm assuming the boat can't cross the river by itself... so, does this work?

1 - Have the SW and Q cross together.
Over = SW & Q
2 - Have the SW cross back over.
Over = Q
3 - Have the Kn and K cross together.
Over = K, Q & Kn
4 - Have the Kn cross back over.
Over = K & Q
5 - Have the Kn and KW cross together.
Over = K, Q, Kn & KW
6 - Have the KW cross back over.
Over = K, Q & Kn
7 - Have the S and SW cross together.
Over = K, Q, Kn, S, SW
8 - Have the SW cross back over.
Over = K, Q, Kn & S
9 - Have the KW and SW cross together.
Over = K, Q, Kn, KW, S & SW
 
  • #8
Rahmuss
222
0
Actually mine has a flaw if you mean that two women can't be alone with a man on EITHER side.
 
  • #9
Dr. Robotnik
5
0
I think I got it:

Let's call them AaBbCc

Aa -> \ BbCc | Aa - Aa(King and queen) goes over first
A <- \ ABbCc | a - A then goes back
bc -> \ ABC | abc - bc goes over to join a
a <- \ AaBC | bc - a goes back
AB -> \ aC | ABbc - AB takes the boat over
Bb <- \ aBbC | Ac - Can't let C alone with c&b
CB -> \ ab | ABCc - CB takes the boat
c <- \ abc | ABC - We need our wives so c goes back to fetch them
ab -> \ c | AaBbC - let's leave c for now
a <- \ ac | ABbC - but then again, we're not mean
ac -> \ | AaBbCc - We're done! Hurray

 
  • #10
EmiR
8
0
knight's wife will take the knigh to the other side. then she will take the queen to the other side and then queen will return. then hmmmmmmmm then the servant and his wife will go to other bank. servant's wife will return take the queen to the other side after that queen will return again and have to take the king.
 
  • #11
einsteinian77
208
0
The king and queen cross over first. Then the queen goes back to pick up the knights' wife and drops herself, the queen, off with her king. The knights' wife then goes back and picks up the knight, the knight gets dropped off with the king and queen. Then the knights' wife goes and picks up the servents' wife. The knights wife is dropped off w/ the king, queen, and the knight. Finally the servents' wife goes back and picks up the servent and and everyone has crossed over. And they live happily ever after...
 
Last edited:
  • #12
devender
4
0
@@einsteinian77: "Then the knights' wife goes and picks up the servents' wife. The knights wife is dropped off w/ the king, queen, and the knight."
When the knights wife returns to pickup servants wife again the equation is one men and 2 wifes so the answer is wrong
 
  • #13
BobG
Science Advisor
Homework Helper
330
84
@@einsteinian77 probably won't ever read your post, since he hasn't visited the forum in nearly 5 years.
 
  • #14
magpies
175
2
Easy queen takes one of the other women then comes back for the last one then queen comes back takes king with her then after having the 3 women on one side the king starts to bring the men over. The trick is that the men won't run away with 3 women on a side only 2. I think.
 
  • #15
devender
4
0
@magpies If your answer was in continuation to what einsteinian77 has written then it would not work in the very first permutation where he mentions that: "The king and queen cross over first. Then the queen goes back to pick up the knights' wife and drops herself, the queen, off with her king." because when the Queen brings back the Knights wife then the king would run away with the queen and Knights wife.

Here goes the Solution for it:

The King and the Knight cross over first, then one of them returns let's say the king to bring the servant. The servant comes back to pick his wife and then both of them get dropped now the servants wife comes to pick the queen and both of them get dropped off at the shore now u have the option of either sending the Knight or any of those 2 womens to bring the Knights wife.
 
  • #16
devender
4
0
@@DeathKnight Can u validate my answer
 
  • #17
davee123
672
4
The King and the Knight cross over first

That won't work. That leaves the Servant on a side all by himself with the 3 women, which he'll run off with.

I solved it, but it took 11 crossings.

DaveE
 
  • #19
ShadowSpirit
1
0
1. King and Queen cross to side 2
2. King comes back to side 1, Queen left at side 2
3. Knight's Wife and Servant's Wife go to and stay at side 2, Queen comes back to side 1
4. Servant and Knight go to side 2, Servant and Servant's Wife comes back to side 1, leaving Knight and his wife at side 2
5. King and Servant go to side 2, Knight's Wife comes back, leaving all the men on side 2
6. Knight's Wife and Queen go to side 2, Queen comes back
7. Queen and Servant's Wife go to side 2, FINISHED
 
  • #20
devender
4
0
That won't work. That leaves the Servant on a side all by himself with the 3 women, which he'll run off with.

I solved it, but it took 11 crossings.

DaveE

It has been mentioned in the question clearly that if there are 2 womens with one men then they would run away he has no where mentioned that if there are more than 2 i., 3 they will run away together. I have given the explanation considering that.anyways @@shadowspirit has solved it considering this scenario as well.
 
  • #21
davee123
672
4
It has been mentioned in the question clearly that if there are 2 womens with one men then they would run away he has no where mentioned that if there are more than 2 i., 3 they will run away together.

Personally, I think it's a poor re-statement of the problem by the OP. I interpreted it that if a man finds himself alone with 3 women, he also is consequently finding himself alone with 2 women, thereby fulfilling the rule, even though, yes, you are correct in that the OP says "if a man finds two women alone", which means that "three women alone" or "one woman alone" is still perfectly valid.

I think the actual problem would probably stipulate that if at any time a man finds himself the ONLY man around (in the boat or on a side), and there are any women present that aren't his wife, he'll run away with them.

DaveE
 
  • #22
Mazer Rackham
4
0
Servant and Servant Wife go over
Servant returns
Queen and Knight Wife go over
Both stay and the Men must swim...

Queen and Servant Wife go over
Queen Returns
Queen and Knight Wife go over
Queen returns
King and Servant go over
Servant Wife and Servant return
Servant and Knight go over
Knight Wife returns
Knight Wife and Servant Wife go over
Knight Wife returns
Knight Wife and Queen go over
All Done!
 

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