The old couple traveled with their son, daughter and a dog. On the way, they must cross a river. There is an empty boat at the ferry, which can carry 50 kilograms at most. The son and daughter each weigh 25 kg, and the dog weighs 10 kg. Excuse me, how can they cross the river safely?

Three monks, a big monk and two little monks are going to the temple across the river. There is no bridge over the river. None of them can swim, but they have just found a boat. The maximum load of this ship is 60 kilograms, 50 kilograms for the big monk and 30 kilograms for the two little monks. How can they arrange the order of crossing the river in the safest way?

The missionary took a cannibal, and the leaders of the A and B tribes each took two followers across the river. When missionaries leave, cannibals will attack people from two tribes, and when the leader of one tribe is absent, the leader of another tribe will attack followers of this tribe. Only missionaries and leaders of two tribes can row boats. How to arrange crossing the river (the boat has no boatman and can only carry two people at a time)?

Three daughters, three sons, a father, a mother, a housekeeper and a dog are going to cross the river. There is only one boat, and only two people can sit at a time. Only adults can row a boat. When mom is away, dad will beat his son. When dad is away, mom will beat her daughter. When the housekeeper is away, the dog will bite. How can I cross the river?