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Put 1.5g impure sodium sulfate (impurities are insoluble in water) into 85.8g water to make a solution. After filtration, add appropriate barium chloride solution to the filtrate to completely reflect and generate 2.33g white solution. Calculate the mass of sodium sulfate in the original mixture
Let the mass of sodium sulfate be xna2so4 + BaCl2 = BaSO4 ↓ + 2nacl42 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 233x & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2.33 G142X = 2332.33gx = 1.42g
Super hard to challenge?
A car goes from place a to place B at a speed of 42 kilometers per hour. When it reaches half of the whole journey in five hours, the car breaks down. Due to the 0.8 hour delay in repair, how many kilometers per hour must the car travel in order to complete the second half of the journey in five hours?
The second half of the journey = the first half = 42 * 5 = 210 km
Required time: 5-0.8 = 4.2 hours
In the second half of the journey, the car has to travel 210 / 4.2 = 50 kilometers per hour
A super difficult math problem
In order to do a good job in water conservancy construction, a village plans to build an 800 meter long tunnel. A construction team undertakes the project and plans to complete it within the specified time. After four days of work, the equipment is improved and the work efficiency is improved. Every day, the canal is dug 10 meters more than the original plan. As a result, the task is completed 2 days ahead of the specified time, and the number of days required to complete the project is calculated
Please write the detailed proof process!
thank you!
It will take X days to finish the work according to the plan
According to the meaning of the title
The original plan is to dig 800 / X meters of canal every day, and the equation can be listed
800/x*4+（800/x+10）（x-4-2）=800
Multiply both sides of the equation by X and sort them out
X & # 178; - 6x-160 = 0, X1 = 16, X2 = - 10 (rounding off)
A: it is planned to take 16 days to complete such work
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