Tonight, Ha's school had a "math night" for kids from k to 2nd grade. Stephen's math skill is much better than mine ( He won something on the National math competition in Taiwan, but I didn't. I was not good enough to even participate in that competition.), but since he needed to eat dinner, I went to the math night with Ha.
It had many sets of different games and puzzles, and kids could freely choose to play with any games or puzzles. We enjoyed most of the games except for one....because we couldn't get the answer. When I came home and asked Stephen, he got the right answer right away. ( I believed that I heard about this question long time ago, but I just couldn't think of the answer .)
Ok, here is the question:
One person and his 3 pets, a dog, a cat, and a bird are going to cross the river by the boat. The boat can only take that person and one of the pets each time. The cat can not be alone with the dog, and the bird can not be alone with the cat. Can you think of a way for all of them to cross the river?
16 則留言:
The bird and the dog can stay together, so the person can take the cat with him first. Then he can take the either the dog or the bird on the second trip. The third trip he can take whatever pet left.
The person can take the dog in the boat and the bird can fly for the first trip. Then the person come back for the second trip to get the cat.
JF: Wrong answer! If he took either a dog or a bird with him on the second trip, that pet will be alone with the cat on the other side of the river, which is a no no.
SF: That's Ha's answer,too, but it's not the best one.
The person can take the cat with him during the first trip.
Then he can come back to get the dog on the second trip. The bird can fly with them during the second trip.
On the best answer, the bird doesn't need to fly...remember, she's a pet, so she needs to be taken care of.
Does the best answer require the dog to swim??? ( I assume if the bird does not fly, the dog does not need to swim....)=)
Exactly. Treat the pet nicely!
I really cannot think of any better answers... I am waiting for you to share the solution.
Doesn't your husband want to try to solve it?
I will ask him when he is back home from the library.
I don't know the answer. I tried to ask Phil to do it, but he did not have time.
Ran's 1 answer: the person first get the cat cross the river, then take the bird, then come back with the cat then take the dog. Last trip he takes the cat with him.
Ran's 2 answer: One trip, the person takes the cat in the boat with him. The bird fly and the dog swim to cross the river.
Congratulations! Ran's answer #1 is the correct answer! We all have smart husbands.
Yes, my hubby is smart. 我常說他的一個頭腦夠我們兩人用!!!
Smart Ran and Stephen! We don't know whether Philip is smart because he refused to participate.
Cheryl's answer is:
The person first takes the cat to across the river. When they get there, he hides the cat in a safe place and no one can see it.
Then he goes back to take the dog and leave the dog there by itself.
Then he goes back to take the bird.
**Even though Cheryl's answer is not the correct answer, but she still wants me to share her answers with you.
Sure, as long as people can think of something logical, it is the right answer even though it may not be the best one. So, Roro got the right answer, too.
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