Some interesting math problems junior high school math

Three people ate 30 yuan together, so each gave it to the waiter 10 yuan. Later, the boss told the waiter that it was a special price today, so he only accepted 25 yuan, so the waiter changed the 5 yuan to the guest, but he changed it from 5 yuan to 2 yuan, and finally only gave it to the guest 3 yuan, which means that each of the three guests only paid 9 yuan. 3x9 = 27,27 and the waiter took 2 yuan's money only 29, but they obviously paid 30 yuan. Who did you give a dollar to?

Answer: The cost for three people is 9X3=27 yuan.

The money actually paid by three people is: 30-3=27 yuan.

2 yuan, the waiter, blackmailed the passengers. The fee that three people should pay is 30-3-2 (the money blackmailed by the waiter) =25.

Li Bai, a great poet in the Tang Dynasty, often drank and wrote poems. The following poem "Li Bai buys wine" is a very interesting math problem:

Li Bai was walking in the street, carrying a pot to buy wine.

When you meet a shop, look through it and see the flowers and wine.

I met the shop flower three times and drank all the wine in the pot.

Please guess, there is wine in the pot.

Why do you want this formula: 1 divided by 2 plus 1, divided by 2 plus 1, and finally divided by 2 equals 7/8 barrels.

Answer: "Have a drink when looking at flowers" means to add a cup when looking at flowers, and "Double it when you meet a shop" means to /2 when you meet a shop.

Then: (0+ 1) divided by 2 plus 1, divided by 2 plus 1, and finally divided by 2 equals 7/8 barrels.

Multiply a two-digit number by 67 and add an integer multiple of 100 to get a number. What is the law of this number?

Answer: Because I don't know how many times it is one hundred, if it is regular, only the last two digits are regular.

Considering that 3× 67 = 20 1, the last two digits are 1. It can be concluded that there will be a one-to-one correspondence between the last two digits of the original number and the final number.

Suppose that the last two digits of this number are x and the first two digits are y;

If 4

If 37

If 70 < = x & lt=99, y = 3 * (x-67)+1;

Or, if the original number is 3*n, the last two digits of the last number are n;

If the original number is 3*n+ 1, the last two digits of the last number are n+67;

If the original number is 3*n+2, the last two digits of the last number are n+34;

N is an integer, which makes the original number into two digits.

One day, a young man came to Boss Wang's shop and bought a present. The cost of this gift is 18 yuan, and the list price is 2 1 yuan. As a result, the young man took out 100 yuan to buy this gift. Boss Wang had no change at that time, so he changed the neighborhood's 100 yuan into 79 yuan and gave it to the young man. But the neighborhood (loss cost 18 yuan, not counting 2 1 yuan).

Answer: Income-expenditure = net profit.

Merchant's income 100 yuan in cash and loans.

How much did the businessman pay?

18 yuan +79 yuan's change+100 yuan to compensate neighbors = 197 yuan.

100- 197 =-97 yuan

So the merchant lost 97 yuan.

Look at it from another angle:

Businessmen, customers and neighbors are a closed system.

Conservation of RMB in the system

The neighbor didn't make a penny, nor did he lose a penny. They lent 100. Really, income 100.

Where are the clients? Things with income of 65438 +08 yuan +79 yuan change = 97 yuan.

According to the law of conservation, businessmen should pay 97 yuan.