A.Shapovalov

River Crossing Puzzles

This is just a small part of my collection of puzzles and problems about crossing a river. Some of them I invented myself. To solve a puzzle one need only a common sence, to solve a problem one should know even something in mathematics.
I'll try to publish a new item or an answer at least once a week.

Try to find a solution before look at the answer. Good luck! By click on a picture, you can play the puzzle online.
The main agreement: When the boat comes to a bank, everybody must land, even when they mean go back.

List of Puzzle Groups: Adults and Children(AC), A Farmer and a Dog(FD), A Farmer and a Goat(FG), Gold in Suitcases(GS), A Heavy Chest(HC), Jealous Husbands(JH), Knights and Pages(KP), Missionaries and Cannibals(MC), Merchants versus Robbers(MR), Old Grandees(OG), Policemen and Refugees(PR), A Round Table(RT), Run Away(RA), Same time(ST), Thieves with Suitcases(TS), Thieves and a Robber(TR), Timid and Pert(TP), Torch on a Bridge(TB), Two Families(TF), Weight Limit(WL)



Level 1(asy): FD1, RT, PR1, MR1, MR2, WL, MC1, ST, KP1, TP1
Level 2: TS1, FG1, FG2, FG3, FD2, A, PR2, FD1, TF1, KP1, OG1, HC, TS2
Level 3: MC2, MC4, RA1, RA2, FD3, GS, MC3, JH1, JH2, JH3, JH4, TB1
Level 4: TB2, TR, KP2, OG2
Level 5(hard):

Some puzzles are composed by me or by my friends and relatives.
Alexander Shapovalov: FD3, PR, TF, TS
Danil Shapovalov: HC



A Round Table
RT. Four persons sat around a table, any two neighbours dislike each other. They all want to get to the other side of a river. There is a small boat, which can fit only two. If two persons dislike each other, they want neither to be in the boat together, nor to be on the same side without any other person. How can they all get to the other side?
Solution



Merchants versus Robbers
MR1. Three robbers came to the left side of a river. At the same time four merchants came to the right side of the river. There is a small boat at the left side, which can fit only two. To prevent a tragedy, there can never be more robbers than merchants together on the same side. How can they all get to the opposite side?
Solution
MR2. Three robbers came to the left side of a river. At the same time three merchants came to the right side of the river. There is a small boat at the left side, which can fit only two. To prevent a tragedy, there can never be more robbers than merchants together on the same side. How can they all get to the opposite side?
Solution



A Farmer and a Goat
FG1. A farmer returns from the market, where he bought a goat, a cabbage and a wolf. On the way home he must cross a river. His boat is small and won't fit more than one of his purchases. He can neither leave the goat alone with the cabbage (because the goat would eat it), nor leave the goat alone with the wolf (because the goat would be eaten). How can the farmer get everything on the other side?
Solution
FG2. A farmer returns from the market, where he bought a goat, a dog, a cabbage and 2 wolves. On the way home he must cross a river. His boat is small and won't fit more than two of his purchases. He can neither leave the goat with anything else, nor a wolf with the dog. How can the farmer get everything on the other side?
Solution
FG3. A farmer returns from the market, where he bought a goat, a dog, a cabbage, a wolf and a big cat. On the way home he must cross a river. His boat is small and won't fit more than two of his purchases. He can neither leave the goat with the wolf or the cabbage, nor leave the dog with the wolf or the cat. How can the farmer get everything on the other side?
Solution



A Farmer and a Dog
FD1. A farmer returns from the market with a dog, a cat, a goose and a basket with grain. On the way home he must cross a river. His boat is small and won't fit more than one of his purchases. The cat cannot be left with either the dog or the goose. The goose can be left with the grain only if the dog is present because the dog will guard the grain and won't eat the goose. How can the farmer get everything on the other side?
Solution
FD2. A farmer returns from the market with a dog, two cats and three geese. On the way home he must cross a river. His boat is small and won't fit more than two of animals. If a cat stays alone with the dog, it'll be fight, but the dog will not attack two cats. Cats will not attack geese only if there are more geese than cats. How can the farmer get everything on the other side without any fight?
Solution
FD3. The same situation as FD2, but the boat fits two animals only if at least one of them is a goose, otherwise it fits only one animal.



Same time
ST. Two men came to a river at the same time. There were a boat at a bank. Both managed to get himself on the opposite side of the river. How can this happen?
Solution



Weight Limit
WL. Three travellers came to a river. There is a small boat, which can bear a load not more the 100 kg. The weight of one traveller is 45 kg, of the other — 50 kg, of the third one — 80 kg. How can they all get to the other side?
Solution



Adults and Children
AC. A group of 5 adults with a couple of children came to a wide river. There was no bridge there. The only way to get to the other side was to ask a fisherman if he could lend them his boat. However, the boat could carry only one adult or two children. How does they all get to the other side and return the boat to the fisherman?
Solution



Thieves with Suitcases
TS1. Three thieves called Rock, Paper and Scizzors came to the left side of a river. Each thief has three big suitcases. If Rock is left alone with any Scizzors' suitcase he will stole goods from the suitcase. Scizzors will do the same thing with Paper's siutcase, and Paper will stole goods from Rock's suitcase. They have a boat, which can fit all three of them without suitcases or two persons with a suitcase or one person with two suitcases. Only Rock can row. How can they all get to the other side with all the luggage intact?
TS2. Three thieves came to the left side of a river. Each thief has two big suitcases. A thief does not want to leave his suitecase with any other person, but it is OK to leave suitcases on a bank with no people there. They have a boat, which can fit all three of them without suitcases or two persons with a suitcase or one person with two suitcases. How can they all get to the other side with all the luggage?
Solution



Gold in Suitcases
GS. Three thieves came to a river. Each has a suitcase with golden bullions. The first one has 2 bullions, the second – 4 bullions, the third – 6 bullions. There is a small boat, which can fit either 2 persons or a person and a suitcase. If a thief is alone in the boat or on a bank with more bullions than he owns, he takes the gold and run away. How can they all get to the other side so that each kept it's own gold?
Solution



Policemen and Refugees
PR1. A refugee and a policeman came to the left side of a river. At the same time a refugee and a policeman came to the right side of the river. They all want to get to the other side of the river. There is a small boat at the left side, which can fit only two. Refugees do not agree if there be more policemen than refugees on the same side. Only persons from the left side can row. How can all 4 of them get to the other side?
Solution
PR2. 4 policemen came to the left side of a river. At the same time a 5 refugees came to the right side of the river. They all want to get to the opposite side of the river. There is a small boat at the left side, which can fit only two. Refugees do not agree if there be more policemen than refugees on the same side. How can they all get to the other side?



Missionaries and Cannibals
MC1. Two missionaries and two cannibals want to get to the other side of a river. There is a small boat, which can fit only two. To prevent a tragedy, there can never be more cannibals than missionaries together on the same side. How can they all get to the other side?
Solution
MC2. Three missionaries and three cannibals want to get to the other side of a river. There is a small boat, which can fit only two. To prevent a tragedy, there can never be more cannibals than missionaries together on the same side. How can they all get to the other side?
Solution
MC3. The problem MC2 with an extra condition: only one missionary and one cannibal can row.
MC4. 50 missionaries and 49 cannibals want to get to the other side of a river. There is a small boat, which can fit only two. To prevent a tragedy, there can never be more cannibals than missionaries together on the same side. How can they all get to the other side?



Run Away
RA1. Three men and three women want to cross a river. There is a small boat, which can fit only two persons. If a man finds two or three women alone on any side he'll run away with them. How can they all get to the other side without somebody run away?
Solution
RA2. Three married couples want to cross a river. There is a small boat, which can fit only two persons. Men cannot take any woman except their wives on the boat. If a man finds two or three women alone on any side he'll run away with them. How can they all get to the other side without somebody run away?



Jealous Husbands
JH1. Three married couples want to cross a river. There is a small boat, which can fit only two persons. Each of three husbands is jealous and will not let his wife to be in the presence of other men if he is not there. How can they all get to the other side?
Solution
JH2. The same question for 4 couples, if there is an island where wives can stay without their husbands.
Solution
JH3. The same question for 4 couples, no island, but the boat fit three persons.
JH4. The same question for 5 couples, with the boat which fits three persons.



Knights and Pages
KP1. Two knights with two pages each came to a river. There is a small boat, which can fit only two persons. Neither knight can leave his page in the boat or on a river bank with another knight. How can they all get to the other side?
Solution
KP2. Two knights with two pages each and a knight with a page came to a river. There is a small boat, which can fit only two persons. Neither knight can leave his page in the boat or on a river bank with another knight or knights. Can they all get to the other side?
KP3. Three knights with two pages each came to a river. There is a small boat, which can fit only two persons. Neither knight can leave his page in the boat or on a river bank with another knight or knights. Can they all get to the other side?



Thieves and a Robber
TR. Two thieves and a policeman with a robber in his custody came at the same time to a river bank. Each thief has two big suitcases. All six of them want to cross the river. There is a small boat, which can fit only two persons or a person and a suitcase. Thieves do not want to be in the boat or on the same bank with the robber if the policeman is not there. A thief does not want to leave his suitecase with the robber without policeman, or with another thief even if the policeman is there. How can they all get to the other side?
Solution



Torch on a Bridge
TB1. One family wants to get over a bridge in the darkness. Dad can make it in 1 minute, mama in 2 minutes, son in 5 and daughter in 10 minutes. Unfortunately, not more than two persons can go over the narrow bridge at one time, moving at the speed of the slower one. How can they all make it to the other side if they have a torch that lasts only 18 minutes and they are afraid of the dark?
Solution
TB2. One family wants to get over a bridge in the darkness. Dad can make it in 1 minute, mama in 3 minutes, one son in 4, the other in 6, daughter in 8 and grandmother in 10 minutes. Unfortunately, not more than two persons can go over the narrow bridge at one time, moving at the speed of the slower one. How can they all make it to the other side if they have a torch that lasts only 32 minutes and they are afraid of the dark?



Old Grandees
OG1. Three grandees of different ages came to the left side of a river. There is a boat with a boatman. The boatman can get grandees one by one to any side or to the island in the middle of the river. But if the boatman come to any place and invites a passenger there must be the oldest among grandees who are there. A grandee can not go out the boat to the bank or to the island if there is an older grandee. The boatman can choose where to go for a passenger and where to get the passenger. How can he get them all to the right side?
Solution
OG2. Same as OG1 for 4 grandees.



A Heavy Chest
HC. Three pirates with a chest came to the left side of a river. There is a boat, which can fit three pirates or two pirates and the chest. But the chest is heavy, it can be loaded into the boat or unloaded only by all three pirates. How can they all get to the other side with the chest?
Solution



Two Families
TF1. Two families came to the left side of a river. Each family consists of father, mother and a doughter. There is a boat, which can fit two persons. Only men can row. A daughter can be on a bank or in the boat with some of her parents. How can they all get to the other side?



Timid and Pert
TP1. Four persons came to the left side of a river. One is timid, one is pert, two are common. There is a boat, which can fit two persons. The timid one refuses to be alone either in the boat or on a bank. The pert one insists to be alone in the boat. How can they all get to the other side?