2. Nine copper coins, one of which is fake, and the authenticity is only different in quality. If you weigh it at least (8 times) with a balance without weight, you can definitely find out the fake copper coins.

There is a warehouse every100km on the highway. * * There are five warehouses. Warehouse 1 yes 10 tons, warehouse 2 has 20 tons, and warehouse 5 has 40 tons. The other two warehouses are empty. Now I want to put all the goods in one warehouse. If every ton of goods is transported 1,

1No. 100 km 2 100 km 3 100 km 4 100 km 5.

10 tons, 20 tons and 40 tons

4. There are 207 students in the sixth grade, 2 boys/11,7 girls take part in the math competition, and the rest are the same number of boys and girls, with 97 girls in the sixth grade.

5. Xiaolan and Xiaoli play guessing games. Xiaolan writes a four-digit decimal on the straight line for Xiaoli to guess. Xiaoli asked, "Is it 603 1?" Xiaolan said, "I guessed the right number, and the location was right." Xiaoli asked again, "Is it 5672?" Xiaolan said: "I guessed both numbers correctly, and neither position is right." Xiaoli asked again, "Is it 4796?" Xiaolan said, "I guessed all four numbers correctly, but the positions were all wrong." Can you infer the four numbers written by Xiaolan from the above information? 6974

6. If 20 rabbits can be exchanged for 2 sheep, 8 sheep for 2 pigs and 8 pigs for 2 cows, how many rabbits can 4 cows be exchanged? 640

7. Light light blue is 8 years old and her father is 38 years old. How old is light light blue? Dad is exactly four times as old as light light blue. 10

8. For the people, every three empty soda bottles can be replaced by 1 bottle. Light light blue bought 99 bottles of soda in the summer vacation, and changed them into empty bottles after drinking them. How many bottles of soda can she drink at most? 147

9. In a division formula, the sum of dividend, divisor, quotient and remainder is 75, the known quotient is 8, and the remainder is 2. What are the dividend and divisor?

58 7

10. There are two iron wires of the same length. The first one is minus 30 cm, the second one is minus 18 cm, and the remaining length of the second one is twice that of the first one. How many centimeters is left in the second wire? 24

There are 1 1, 1, 2, 3, 4, 5, 6, 7, 8 and 9 cards, each with three cards. A said, "The product of my three cards is 48", and B said, "The sum of my three cards is 65438.

238 564 179

/kloc-how many different rectangles can a 0/2.24cm long iron wire enclose (the length and width are all whole centimeters, not counting joints)? What are the areas? Compare it again. What can you find? six

13 Master Zhang is used to taking two days off every five days of work. Recently received the task of producing 330 parts, and he produces 30 parts every day. How many days will it take to finish this task at least? 15

14 On Sunday, Xiaohui took a taxi to visit her grandmother 8 kilometers away. When taking the bus, he saw the fare table on the taxi: 8 yuan within 5 kilometers; How much does 2 yuan Xiaohui have to pay to go to grandma's house?

14

15, a decimal, if you expand its decimal part by 4 times, you will get 5.4; If you enlarge its decimal part by 9 times, you get 8.4. What is this decimal? 3、6

16, average height of Party A and Party B 1.66m, average height of Party B and Party C 1.7m, average height of Party A and Party C 1.65m, what is the average height of Party A, Party B and Party C?

1.67

17, the sum of a, b and c is 270. A is three times that of B, and B is twice that of C. What are the numbers of A, B and C respectively?

180 60 30

18. There are two coal yards A and B. The coal storage capacity of coal yard A is three times that of coal yard B. If 180 tons is transported from coal yard A to coal yard B, the coal storage capacity of the two coal yards is equal. How many tons are there in coal yard A and coal yard B respectively?

540 180

19, five players line up to do exercises, among which 1 new players can't stand at the head. How many different ways are there?

96

There are 50 students in Class 20.6 (1). There are 25 swimmers, 28 gymnasts and 5 non-gymnasts. How many students can swim and do gymnastics? eight