A person who can climb one, two or three steps in a single leap is trying to climb a stairway. The stairway consists of 25 steps. In how many different ways can he climb this stairway?
If the question was asked for a stairway consisting of 4 steps, the answer would be 7 (1-1-1-1, 1-1-2, 1-2-1, 2-1-1, 2-2, 1-3, 3-1).
一个人上台阶的方式有三种,一次跨1、2、3步,那么他要上25步台阶的方法有多少种。
例如,上4步的方法有7种,(1-1-1-1, 1-1-2, 1-2-1, 2-1-1, 2-2, 1-3, 3-1)。
2.Transporting Water
You are in a camp. You want to transport 90 liters of water to your campsite, which is 20 kilometers away. Your carrying capacity is 30 liters and you consume 2 liters of water for every kilometer. What is the maximum amount of water you can bring to the campsite, in liters?
You have a sufficient number of jerrycans and you can release and take on jerrycans
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运水
野营地距离你现在的位置20公里,有90升水,你一次承载的能力是30升,每公里消耗水2升,问最多能带去多少升水到营地。
你有足够多的容器,可以沿途丢弃。
3.Yes-No
Persons A, B, C and D have taken a test which consists of 10 yes-no questions. Every correct answer brings 1 point. The table shows the answers of A, B, C, D and the final scores of A, B and C. Find the final score of D.
A,B,C,D四人做10道回答是否的问题,答对了得一分,四人的答案和A,B,C的得分如图所示。
问D的得分是多少。
4.Boat
Persons A, B, C, D and E would pass across a river using a boat.
• The boat can carry at most two people.
• When using the boat alone, the time required to pass across is 11 minutes for A, 7 minutes for B, 4 minutes for C, 2 minutes for D and 1 minute for E.
• When two people are on board, the time required to pass across is the difference between the times required for each of them to pass across alone.
In how many minutes in minimum can all pass across the river?
Example: If they use the boat as AB,A,AC,B,BD,C,CE they can pass across in 41 minutes (4+11+7+7+5+4+3=41).
A,B,C,D,E五人用一条船过河。
船最多一次乘坐两人。
单独乘坐过河所需要的时间:A :11分钟,B:7分钟,C:4分钟,D:2分钟,E:1分钟。
两个人乘坐时所需要为两个单独过河所需时间之差。
例如:
按如下秩序过河:AB,A,AC,B,BD,C,CE ,则他们所需的时间为41分钟:
(4+11+7+7+5+4+3=41)
问最短多少时间能过使得所有的人都过河。
5.Pattern
How many different patterns can be formed by blackening 3 squares of a grid consisting of 5x5 squares?
Note : If a pattern can be produced by rotating another pattern (90, 180 or 270 degrees) then these two patterns are not considered as different.
题目的意思就是5*5的格子里面放3个块,形成的图案一共有过少种。
其中如果可有旋转而重复的算是同一种。镜像的不算同一种。


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