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People's education printing plate eighth grade second volume mathematics engineering problem examination questions
1 Grade 8 students go to places 10 kilometers away from the school. Some students go by bike first. Twenty minutes later, other students left by car and arrived at the same time. As we all know, the speed of a car is twice that of a bicycle. Seek the speed of riding students.

Solution: If the speed of the cyclist is X, the speed of the car is 2X.

10/X- 10/2X = 1/3

X= 15

So the speed of cycling students is 15km per hour.

Type one.

1. Students from Class Two, Grade Eight take part in tree planting activities. It is known that Class A plants more trees per day 15 than Class B, and the number of days required to plant 90 trees in Class A is the same as that required to plant 60 trees in Class B.. How many trees does Class A plant every day?

2. A forest farm originally planned to fix sand and afforest 240 hectares in a certain period of time, but the actual area of fixing sand and afforesting every day is 4 hectares more than the original plan, and the task is completed five days ahead of schedule. How many hectares of sand fixation and greening are planned every day?

Type 2

Both are 1. Robots are used to carry chemical raw materials. Robot A carries 20kg more per hour than robot B, and the time for robot A to carry 1000kg is equal to that for robot B to carry 800kg. How many chemical materials do these two robots transport per hour?

Both A and B robots are used to carry chemical raw materials. Robot A carries 30 kilograms more per hour, and the time for robot A to carry 900 kilograms is equal to the time for robot B to carry 600 kilograms. How many chemical materials do these two robots transport per hour?

Type 3

1. Two buyers, Party A and Party B, went to a feed company to buy feed twice, and the price of the feed twice was M yuan/kg and N yuan/kg respectively (M, N is positive, and m n is positive). Moreover, the purchase methods of the two buyers are different. Among them, A buys 1000 kg every time, and B uses it in 800 yuan every time, regardless of how much feed to buy.

(1) What is the average unit price of feed purchased by Party A and Party B?

(2) Whose purchase method is more cost-effective?

2. Party A and Party B buy grain twice in the same grain store at the same time (assuming the unit prices of the two purchases are different). Every time Party A buys 100 kg of grain, Party B spends 100 yuan each time. Suppose that the unit price of grain purchased by Party A and Party B for the first time is X yuan/kg, and that for the second time is Y yuan/kg.

(1) Please use an algebraic expression containing x and y: A buys twice the amount of grain payable * * *; Party B buys two kilograms of grain. If the average unit price of grain purchased by Party A and Party B is C 1 yuan per kilogram and C2 yuan per kilogram, then C 1 =, C2=.

(2) If it is stipulated that whoever buys grain twice will have a lower unit price, then the way to buy grain will be more cost-effective. Please communicate with your partner to judge which way to buy grain is more cost-effective and explain the reasons.

Improve the problem

1. Liyuan Development Company's 960 new product needs to be finished before it can be put on the market. At present, both Factory A and Factory B want to process these products. It is known that it takes more than 20 days for Factory A to process these products alone, and the daily processing capacity of Factory A is the same as that of Factory B.. The company will pay 80 yuan's processing fee to Factory A and to Factory B 120 yuan every day.

(1) Q: How many new products can Factory A and Factory B process every day?

(2) The product processing scheme formulated by the company is as follows: it can be completed by each manufacturer alone or jointly by two manufacturers; During the processing, the company sends engineers to the factory for technical guidance every day, and pays 5 yuan a meal allowance every day. Please help the company choose a solution that saves time and money, and explain the reasons.

2. The calculation method of water fee of a water supply company is as follows: the monthly water consumption of each household does not exceed 5, and the fee is 1.5 yuan per cubic meter; If the monthly water consumption of each household exceeds 5%, a higher fixed fee will be charged per cubic meter for the excess. On June 65438+ 10, the water consumption of the Zhang family was that of the Li family, that of the Zhang family was 17.5 yuan, and that of the Li family was 27.5 yuan. Q: What is the charge per cubic meter for the part exceeding 5?

1. Two buyers, Party A and Party B, went to a feed company to buy feed twice, and the price of the feed twice was M yuan/kg and N yuan/kg respectively (M, N is positive, and m n is positive). Moreover, the purchase methods of the two buyers are different. Among them, A buys 1000 kg every time, and B uses it in 800 yuan every time, regardless of how much feed to buy.

(1) What is the average unit price of feed purchased by Party A and Party B?

(2) Whose purchase method is more cost-effective?

2. Party A and Party B buy grain twice in the same grain store at the same time (assuming the unit prices of the two purchases are different). Every time Party A buys 100 kg of grain, Party B spends 100 yuan each time. Suppose that the unit price of grain purchased by Party A and Party B for the first time is X yuan/kg, and that for the second time is Y yuan/kg.

(1) Please use an algebraic expression containing x and y: A buys twice the amount of grain payable * * *; Party B buys two kilograms of grain. If the average unit price of grain purchased by Party A and Party B is C 1 yuan per kilogram and C2 yuan per kilogram, then C 1 =, C2=.

(2) If it is stipulated that whoever buys grain twice will have a lower unit price, then the way to buy grain will be more cost-effective. Please communicate with your partner to judge which way to buy grain is more cost-effective and explain the reasons.

Improve the problem

1. Liyuan Development Company's 960 new product needs to be finished before it can be put on the market. At present, both Factory A and Factory B want to process these products. It is known that it takes more than 20 days for Factory A to process these products alone, and the daily processing capacity of Factory A is the same as that of Factory B.. The company will pay 80 yuan's processing fee to Factory A and to Factory B 120 yuan every day.

(1) Q: How many new products can Factory A and Factory B process every day?

(2) The product processing scheme formulated by the company is as follows: it can be completed by each manufacturer alone or jointly by two manufacturers; During the processing, the company sends engineers to the factory for technical guidance every day, and pays 5 yuan a meal allowance every day. Please help the company choose a solution that saves time and money, and explain the reasons.

2. The calculation method of water fee of a water supply company is as follows: the monthly water consumption of each household does not exceed 5, and the fee is 1.5 yuan per cubic meter; If the monthly water consumption of each household exceeds 5%, a higher fixed fee will be charged per cubic meter for the excess. On June 65438+ 10, the water consumption of the Zhang family was that of the Li family, that of the Zhang family was 17.5 yuan, and that of the Li family was 27.5 yuan. Q: What is the charge per cubic meter for the part exceeding 5?