Fun math puzzles

Group A:

1. The two brothers took turns counting. The brother counted odd numbers each time, counting 1 for the first time, then 3, 5, 7, 9, 11, 13, and 15. Every time I count even numbers, I count 2 for the first time, then 4, 6, 8, 10, 12, 14, and 16. Please answer quickly. How much smaller is the sum of the 8 numbers in your brother's number than the 8 numbers in your brother's number?

2． Two adjacent even numbers are multiplied by a certain number respectively, and the two resulting products differ by 100. Ask what a certain number is?

3. Among the hundred numbers from 1 to 100, there are ( ) pairs where the divisor quotient of two numbers is 2. Among them, the pair with the smallest dividend and divisor is ( ) and ( ), and the pair with the largest dividend and divisor is ( ) And how many?

4. Fold a rope in half, then fold it in half again, and then cut it in the middle. How many pieces can it be cut into?

5. Mom said to Xiaoqin: "I will give you 9 cents. You can go to the post office to buy stamps. There are only three types of stamps: 3 cents, 4 cents, and 8 cents. The number of each is the same." Ask Xiaoqin how much he can buy back. How many stamps?

6． Choose 5 numbers from the six numbers 8, 9, 16, 19, 23 and 27, so that the sum of three numbers is twice the sum of the other two numbers. How should I choose?

7. The product of a number multiplied by 4 is 900 less than the product multiplied by 40. What is this number?

8． The sum of number A and number B is greater than the sum of number A and number C by 3. What is the difference between number C and number B?

Group B:

9. Divide 100 into the sum of 12 numbers so that each number contains the number "3". How to divide?

10. There are 9 balls in the pocket, each ball is marked with a number, which are 1, 2, 3, 4, 5, 6, 7, 8, and 9. Four people A, B, C, and D each take out two balls from their pockets. The sum of the numbers of the two balls taken by A is 10, the difference between the numbers of the two balls taken by B is 1, and the product of the numbers of the two balls taken by C is 24. , the quotient of the two balls taken by D is 3. Excuse me, what number is marked on the remaining ball in the pocket?

11. There are 22 common forest animals in the circus. 22 animals have 40 legs. Animals with 2 legs are twice as many as animals with 4 legs. How many animals are there with two legs? (Note: There are also snakes without legs)

12. Each of the five brothers has some candies, the larger ones are more numerous than the smaller ones. The boss will give some of his own to everyone, and whoever has as many pieces will be given as many pieces as he wants; then the second child will give some of the existing pieces to everyone, and whoever has the current number will be given as much as the third, fourth, and oldest. Five did the same thing; in the end, each of the five people had 32 pieces of candy. How many pieces of candy did each have?

Group C:

13. Mavericks said to people: "Yesterday, I played chess with two chess masters. There were two chessboards in front of me. I played two chess games by myself and competed with these two masters at the same time. Guess who won and who lost? "You must have lost both games." People know that Maverick has just learned to play chess and can't even remember how to move the horse. "No. The first time, both games were draws. The second time, I lost one game and won the other. No matter how many times I play, I will never lose two games at the same time." "You are bragging."

Two chess masters came out to prove: Mavericks did not brag, and we did not concede the chess piece. It was he who used clever methods to play chess with us. What a clever trick Maverick used.

14. I prepare 2 yuan to buy something. As long as it does not exceed 2 yuan, no matter how much the item is, I can get the right amount without the need for change from the salesperson.

But I don’t want to bring a lot of change, and I am required to bring only the minimum coins and banknotes. So, how many coins should you bring at least? How many banknotes should you carry at least?

15. 1×2×3×…×48×49×50=? Multiply fifty numbers from 1 to 50, and the product is a very large number. It is very difficult to calculate with a pen, but with an electronic computer, you can quickly figure out that this is a 65-digit number. This 65-bit number has many zeros at the end.

Now please do some math, how many zeros are there? (Note: not 10 zeros)

Answer:

Group A: 1.8; 2.50; 3.50 pairs, 2 and 1, 100 and 50; 4. 5 segments; 5.90÷(3 4 8) = 6, 6×3 = 18 pieces; 6. (8 19 23) ÷ (9 16) = 2 (times); 7. 900 ÷ (40-4) = 25; 8. The number B is 3 greater than the number C.

Group B: 9.100=30 30 13 3 3 3 3 3 3 3 3 3; 10.7; 11. As can be seen from the question, animals with two legs and animals with four legs have the same number of legs, 40÷2=20 (feet), 20×2=19 (feet); 12. Analyzed by the reduction method, 80, 41, 21, 11, and 6 pieces were found.

Group C: 13. For the sake of convenience, let’s give the two chess players two names: one is Gao Ming and the other is Bi Sheng. In the game of chess played by Mavericks and Gao Ming, Gao Ming made the first move; in the other game of chess, Bi Sheng made the move. Then, the Mavericks saw how Gao Ming would move, and then copied it to deal with Bi Sheng. Then they watched what move Bi Sheng took, and then moved back to deal with Gao Ming. In this way, it seems that Mavericks is playing two games at the same time, but in fact it is Gao Ming and Bi Sheng who are playing against each other. Gao Ming and Bi Sheng cannot win at the same time, and the Mavericks will not lose both sets. 14． Coins: 1 cent for 1 cent, 2 cents for 2 cents, 1 cent for 5 cents*4 coins; banknotes: 2 for 1 dime, 1 for 2 cents, 1 for 50 cents, 1 for 1 yuan*5. 15. Among the fifty numbers from 1 to 50, there are five numbers with 0 at the end: 10, 20, 30, 40, and 50. The multiplication product has 6 zeros at the end; the numbers with 5 at the end are 5, 15, and 25. , 35, and 45 are five, and when multiplied by an even number without 0 at the end, there are 6 zeros at the end of the product. Therefore, this 65-bit number has 12 zeros at the end. (Note: 50=5×10, 25=5×5).

In addition:

1. After putting three identical squares into a rectangle, the perimeter of the rectangle is 60 cm less than the sum of the perimeters of the original three squares. What is the original area of ??each square? (After combining three identical squares into a rectangle, the perimeter of the rectangle is 60 cm less than the sum of the perimeters of the original three squares, which is equivalent to missing the perimeter of a square, so the side length of a square is 15 cm. It turns out that the area of ??each square is 15*15=225 square centimeters)

2. In the pond, the area of ??a lotus leaf will double every day compared to yesterday, covering the entire lotus in 30 days. pond. So, how many days can this lotus cover half of the pond?

(29 days, because it doubles in one day, so it doubles in one day of retreat)

3. It is known that there are 12 small balls with the same shape and appearance, among which there are One is a defective product. Now I give you a scale without weight and weigh it three times. Find out the defective product and find out whether the defective product is heavier or lighter than the genuine product? (Here we assume Dlt; E, then one of E must be a defective product, and we can know that the defective product is heavier than the genuine product. F (10)------- G(11) If F ==G Then 9 is a defective product, and the defective product is heavier. Then one of 6, 7, and 8 must be a defective product, because when we weigh it for the first time, we know H lt; I, so that is It is said that the defective product is on the heavier side. Take any two out of 6, 7, and 8 and weigh them a third time, and the results will come out.)

Make up your own answer:

1. A bottle of soda costs 1 yuan. After drinking, two empty bottles are exchanged for one bottle of soda. Question: You have 20 yuan. How many bottles of soda can you drink at most?

2. Ten numbers, one 89, two 88, three 90, four 91, what is the sum?

3. This is an unfinished equation: 1234567=100. Please insert two minus signs and a plus sign to make them a complete equation.

4.●●●●●○○○○○

1 2 3 4 5 6 7 8 9 10

As shown in the picture above, 1- Cup No. 10 is the same size, among which cups No. 1-5 are filled with red wine, and cups No. 6-10 are empty. Please tell me how many cups should be moved at least so that the full and empty cups can be arranged alternately. (As shown below)

●○●○●○●○●○

5. There are two caves, one of which has treasures and the other does not. There are two people in the world who know which cave contains the treasure, and of the two people, one must tell the truth and the other must lie. Question: How can we ask these two people to know the cave where the treasure is hidden?

6. I have a 1 yuan card and a 10 yuan card. You must tell the truth before I will give you the money (you can give 1 yuan or 10 yuan). If you lie, I will not give you the money. Give you money. What should you say if you want to get 10 yuan?

7. There are 80 balls. One of the fake balls is lighter than the real ball. How can you find the fake ball by weighing it only 4 times using a weightless balance?

8. Can an 11 cm long ruler be engraved with only 3 integer scales, so that it can be used to measure the length of any integer centimeter long object between 1 and 11 cm? If possible, what scales should be engraved?

9. Put an egg into a glass filled with water, and then pour a little hydrochloric acid along the wall of the glass. At this time, the egg will sink and float in the water. What is the reason?

10. A cinema has 2,000 seats. Two movies, A and B, are shown on the same day. There are 1,800 people watching movie A and 1,080 people watching movie B. How can I sit in it and watch it on this day? What is the maximum number of seats in slices A and B? What is the minimum number?

Math puzzles

The idea of ??math puzzles comes from the 14-year-old "Xiao Shuai".

We have four numbers: 1 2 3 4

Combine them into a mathematical equation so that the answer is 5. For example:

4 3 - 2 * 1 = 5

Another established equation using the same numbers is as follows:

4 3 - 2 / 1 = 5

Can you create another mathematical expression that uses 1, 2, 3, and 4 on the left-hand side of the equation and makes the right-hand side equal to 5?

We can use 4 standard mathematical operators:

Add

- Subtract

* Multiply

/ Division

The normal operator rules apply here: multiplication and division first, then addition and subtraction, and operations are performed from left to right. For example:

3 4 * 2 = 11 (not 14) and

8 4 / 2 = 10 (not 6)

You can use brackets to change this order of operations. For example:

(3 4) * 2 = 14

(8 4) / 2 = 6

Here is another solution to our puzzle :

(4 1) / (3 - 2) = 5

There are many more solutions. You can try it.

Here are some examples to try. Insert mathematical operators between the numbers on the left. The same operator can be used multiple times. If necessary, parentheses can also be used. Some puzzles have unique answers. But some have more than one.

5 5 5 1 = 24

3 5 8 2 = 2

9 9 3 6 = 2

5 6 7 8 = 1

4 4 4 3 = 4

2 3 5 7 = 7