Second grade mathematics application problem (set element, column equation and equation solution) thank you ~ mathematics good help Ha, very difficult 1. a factory plans to complete the production tasks of 3 million machines within a certain period of time. After adjusting the original plan, the total amount will increase by 20% on the basis of the original plan and 6 months ahead of schedule. It is estimated that the new plan must be produced 50 thousand times more than the original plan. 2. Xiaojie deposits the 400 yuan earned by work study program into the bank one year at a fixed time. When it matures, he takes out 50 yuan to buy school supplies. The remaining principal and interest are all used to buy a one-year bond. The annual interest rate of the bond is 2.5 percentage points higher than that of the deposit. In this way, Xiaojie can get a total of 378 yuan of principal and interest after the maturity, and calculate the annual interest rate of the bond. (excluding interest tax) 3. A section of road maintenance project on a certain highway is ready for external bidding. There are two engineering teams a and B bidding, and the bidding information says: if the two teams cooperate, it can be completed in six days, and the total project cost is 10200 yuan; if they are completed alone, team a will spend five days less than team B, but team a will spend 300 yuan more than team B, so as to save money. Choose one team, which team

Second grade mathematics application problem (set element, column equation and equation solution) thank you ~ mathematics good help Ha, very difficult 1. a factory plans to complete the production tasks of 3 million machines within a certain period of time. After adjusting the original plan, the total amount will increase by 20% on the basis of the original plan and 6 months ahead of schedule. It is estimated that the new plan must be produced 50 thousand times more than the original plan. 2. Xiaojie deposits the 400 yuan earned by work study program into the bank one year at a fixed time. When it matures, he takes out 50 yuan to buy school supplies. The remaining principal and interest are all used to buy a one-year bond. The annual interest rate of the bond is 2.5 percentage points higher than that of the deposit. In this way, Xiaojie can get a total of 378 yuan of principal and interest after the maturity, and calculate the annual interest rate of the bond. (excluding interest tax) 3. A section of road maintenance project on a certain highway is ready for external bidding. There are two engineering teams a and B bidding, and the bidding information says: if the two teams cooperate, it can be completed in six days, and the total project cost is 10200 yuan; if they are completed alone, team a will spend five days less than team B, but team a will spend 300 yuan more than team B, so as to save money. Choose one team, which team

1. Suppose that the original plan is to produce X 10000 units per month, 300 * (1 + 20%) / (300 / x + 5) + 6 = 300 △ x, and then calculate X. 2. Suppose that the annual interest rate of bank deposit is x-easy-to-get relationship [400 (1 + x) - 50] (1.025 + x) = 373. It takes x (x > 0) days for Party A to complete the project, and the engineering cost is y yuan per day