21. Preparing for the test

1 has two blind people. Each person buys two black so and two white so. But after buying them, they mixed up the sock. The eight so have the same color except for the different colors. Each pair of sock is associated with a trademark. How can I get two black so and two white so for every blind person? [Wanji technology test]

Tip: Get each pair of sock and separate the trademark, one person and one person. Every blind person will get two white so and two black so.

2. You hire a hourly worker to work for you. After 7 days, you use a gold bar as your salary. The gold bars are evenly divided into 7 segments, but they are connected. You must pay for the hourly work. You can only break the gold bars twice. How do you split the gold bars? [Wanji technology]

4 + (2 + 1)

3. How can we achieve a number × 7 as quickly as possible? NVIDIA written examination]

Shift the number three places to the left (equivalent to multiply by 8) and then subtract itself.

4. There are 100 closed doors, and then the status of the switch door is changed [when the door is open, the door is closed, and the door is closed]. For the first time, the status of all doors is changed [when all doors are opened]. the second change is the state of all doors in multiples of 2, the third change is the state of all doors in multiples of 3, and so on until 100th. Finally, what doors are open?NVIDIA written examination]

 1 4 9 16 25 36 49 64 81 100

In fact, it is to find the public factor. If there are even public factors, it is off. If there is an odd number of public factors, it is open.

5, 4 9, how to calculate 100?99 + (9/9) = 100