Looking for math problems like this

A man went to buy onions.

People who ask how much a kilo of onions costs say 1 yuan 1 kg, which means 100 kg, which means 100 yuan.

The person who bought the onion asked the person who sold the onion to sell it separately, saying that the onion was sold at 73 cents.

Everyone who bought onions bought 50 kg of scallions and 50 kg of scallions.

The final calculation is that 50*7 onions are equal to 35 yuan 50*3 onions are equal to 15 yuan, and 35+ 15 is equal to 50 yuan.

The person who bought the onion gave it to the person who sold it, and 50 yuan was left. The person who sold the onion wondered why he wanted to sell the onion 100 yuan.

And why do you buy onions for 50 yuan? Why do you think this is?

Answer: 1 yuan a catty means that no matter whether it is scallions or shallots, it is one yuan a catty. It was 73 cents when he bought the green separately. In fact, its weight has not changed, but the unit price has changed. Green onions are less than 3 cents per catty, green onions are less than 7 cents per catty, and I bought them for 50 yuan at last.

(3) There is a well 7 meters deep.

A snail climbed up from the bottom of the well.

Climb 3 meters during the day and drop 2 meters at night.

How many days does it take for a snail to climb out of the well?

Answer: 5 days.

Many people say that this problem is not to be thought about for seven days ... in fact, in a very simple way. ..

You draw it with a piece of paper, and it will come out .. This question is very simple. ...

(4). A peach with ten cents.

Three peaches for one peach.

1 yuan How many peaches can you eat?

Answer: 1 yuan buys 10, and there is still 10 left after eating. Change three more peaches and eat the remaining four stones.

Change 1 peach, and there are 2 stones left after eating. There are/kloc-0 peaches on credit, and there are still 3 stones left after eating. Give all the cores to the peach seller and the credit.

So, you ate10+3+1+1=15 peaches.

This is a well-known method. There's another way. ..

Don't buy ten at once. Buy separately. ..

Three for the first time, two for the second time and two for the third time. This is ... very simple ... and it's 15.

(5) There are twelve ping-pong balls with the same shape and size, and only one of them is different in weight from the other eleven. Now it is required to weigh the ball three times with an unweighed scale, find out the ball with abnormal weight and know whether it is heavier or lighter than the other eleven balls.

A: divided into A B C 3 groups, with 4 capsules in each group.

There may be three results for the first time. ..

A>B or A=B or a

If A is greater than B, just say that two of the four balls of A are on one side, so that you can know which side is heavier and which side is the heaviest!

If A is equal to B, call the four balls of C directly. The method is as above.

If A is less than B, directly call B's four balls, as above.

(6) A businessman riding a donkey has to cross the desert of 1000 km to sell 3,000 carrots. It is known that donkeys can carry 1000 carrots at a time, but eat 1 carrot every 1 km. Q: How many carrots can a businessman sell at most?

Answer: 534.

First, camel 1000 radish goes forward x 1 km, puts down 1000-2*x 1 radish, and then takes back the rest x 1 radish;

Then camel 1000 radish, take x 1 radish at x 1 km, and let donkey camel 1000 radish;

Continue to the distance of x2 kilometers from the starting point, put down 1000-2*(x2-x 1) radish and return.

Just eat up the radish at the position of x 1 km, and then take x 1 radish back to the starting point;

Finally, the camel took a thousand radishes and walked to x 1, and x2 took all radishes in turn, and then walked to the end.

The remaining radishes at x 1 and x2 are less than or equal to x 1 and (x2-x 1) respectively. Under the constraint of this inequality, it is enough to find the maximum of two remaining radishes, because in fact, the number of two remaining radishes is the number of radishes that can finally reach the end point.

Finally, x 1=200, x2= 1600/3.

The total distance traveled by the donkey is 2 * x1+2 * x2+1000 = 2466+2/3, which means that only one radish can be eaten after walking one kilometer, that is, the total number of radishes eaten is rounded to 2466, so the remaining radishes that can be sold are 3000-2466=534.

It is said that one day the pirate ship was hit by a cow that fell from the world, and five unlucky guys had to flee to an isolated island and find it alone. Fortunately, there is a coconut tree and a monkey! Everyone picked all the coconuts and put them together, but it was late, so we went to bed first.

A guy got up quietly at night, quietly divided the coconut into five parts, found that there was an extra coconut, so he gave it to the lucky monkey, then quietly hid one part, then mixed the remaining coconuts together and put them back in place, and finally quietly fell back to sleep.

After a while, another guy quietly got up and quietly divided the remaining coconut into five parts. As a result, he found an extra coconut and gave it to the lucky monkey. Then he quietly hid a part, mixed the remaining coconuts together and put them back. Finally, he quietly dripped back to sleep.

After a while. ......

After a while. ...

In short, all five people stood up and did the same thing. Everyone gets up in the morning and shares coconuts with ulterior motives. This monkey is really unlucky, because after dividing the coconut into five points this time, there is another coconut, so we have to give it again. The question is, how many coconuts are there in this pile?

Answer: This pile of coconuts is at least 1562 1.

The first man gave 1 monkey, hid 3 124 monkeys and left 12496 monkeys.

The second man gave 1 monkey, hid 2499 monkeys, and left 9996 monkeys.

The third person gave 1 monkey and hid 1999 monkeys, leaving 7996 monkeys.

The fourth person gave 1 monkey and hid 1599 monkeys, leaving 6396 monkeys.

The fifth person gave 1 monkey, hid 1279 monkeys, and left 5 1 16 monkeys.

Finally, everyone divided it into five parts, each 1023, and the extra 1 was given to the monkey.

There is a treasure on an island. When I saw three islanders, I knew that the big islander knew whether the treasure was on the mountain or under the mountain, but sometimes he told the truth and sometimes he lied. Only Nakajima people know whether Oshima people are telling the truth or lying, but Nakajima people themselves tell the truth when the previous person tells the truth and tell lies when the previous person tells lies. Two islanders raise their left or right hands to indicate whether they are right or not, but you don't know which hand indicates yes and which hand indicatesno. But he always tells the truth or lies, and you don't know which of these two types he is. Can you ask whether the treasure is on the mountain or under the mountain with the least number of questions? Tip: If you ask an islander where the treasure is, he will ask how you know where it is. Equal to asking in vain)

A: For convenience, we refer to all the islanders as ABC (actually, C is not used).

The first question asks A: Is the treasure on the mountain?

The second question is B: Is A correct?

The third question is B: 1+ 1 = 2, right?

Ok, now the first question is, we don't know whether A answered "yes" or "no" or whether A answered "yes" or "no". We only know whether A raised his hand with his left or right hand, so we leave him alone.

Look at the second question. No matter whether A's answer is "yes" or "no", as long as A's answer is correct and B is correct in the second question, then he should answer "yes" (if he can speak Chinese).

Still the same. Whether A's answer means "yes" or "no", as long as A's answer is wrong and B's answer is wrong on the second question, he should still answer "yes".

So anyway, B's raised hand means "yes";

The third question: since we know what the right hand means, we can determine whether A is true or false as long as we know whether B's answer just now is true or false, because the truth of both must be the same. So just ask a question, like 1+ 1=2, right?

There is another way:

First of all, ask anyone: Are you telling the truth?

That person will definitely raise the hand that represents yes.

Because if he is telling the truth, he will raise his hand to show yes.

What he said is a lie, and he will raise his hand to show yes.

So it can be concluded that the hand represents

Then ask the China islanders: Did the big islanders say that the treasure is on the mountain?

China islanders must have answered correctly.

In other words, the treasure is where the China islanders say it is.

Because if the China Islanders agree,

If the big islanders are telling the truth, then the China islanders are telling the truth, so the treasure must be on the mountain.

If what the big islanders say is a lie, then what the China islanders say is also a lie. In fact, the big islanders said that the treasure was under the mountain, but because it was fake, the treasure was still on the mountain.

(9) How many tables and people are there in a room?

If there are three people at a table, there are two more.

If there are five people at a table, there are four more.

If there are seven people at a table, there are six more.

If there are nine people at a table, there will be eight more.

If 1 1 one table for each person, that would be just right.

How many people are there in this room?

Answer: 25 19 people. As long as it is 315× (11x+8)-1.

Because 9 is three times that of 3, 3 doesn't count.

According to the topic, we can draw a rule.

Is a multiple of 5, 7 and 9, MINUS one.

So 5×7×9=3 15.

Then calculate the multiple of 3 15 divided by the period 1 1.

The period is: 731062951840 * *1,because there is a simple algorithm without trying one by one.

Because 3 15- 1 is divisible by 1 1 .. so we take the periodic remainder of 1.

(10) Someone wants to buy some tableware. After going to the tableware shop, they found that they could buy 2/kloc-0 forks and 2/kloc-0 spoons or 28 knives with their money. If the number of forks, spoons and knives he bought is not uniform, he can't match the whole set, so he must buy the same number of forks, spoons and knives, just to run out of money. What would you do if you were this person?

Answer: You can buy 12 set tableware.

The money for a spoon and fork is 1/2 1, and the money for a knife is 1/28. ..

A set of total price1/21+1/28 =112. ..

So you can buy 12 sets ... all the money is used up.

The police found a thief.

The police chased the thief and the thief ran away.

Running and running, there is a river ahead.

This river is 12 meters wide, and there is a tree on the thief and policeman side of the river.

The height of the tree is 12 meters, and all the leaves on the tree are gone.

The thief was wearing a 6-meter-long collar.

Ask the thief how to cross the river.

Answer: Tie the scarf to the top of the tree, and the thief will hang the scarf and swing it.