An engineering team built a 1200 meter long highway, which took 8 days to build 4 / 15 of the total length. According to this calculation, how many days will it take to complete the highway

An engineering team built a 1200 meter long highway, which took 8 days to build 4 / 15 of the total length. According to this calculation, how many days will it take to complete the highway

It will take X days
1200×4/15：8=1200：x
320：8=1200：x
320x=9600
x=30
A: it will take 30 days to complete the road
Solution 2: 1200 × 4 / 15 = 320m
320 △ 8 = 40m
1200 △ 40 = 30 days
A: it will take 30 days to complete the road

What is the function of the clear water pool of the waterworks

The function of the clean water tank is to make the filtered clean and clarified filtered water flow along the pipeline to its internal storage, and add liquid chlorine into the clean water again for disinfection for a period of time, so as to kill the bacteria, Escherichia coli and other bacteria in the water body and achieve the effect of sterilization
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There is a small waterworks with 450 tons of water in the reservoir. The waterworks can inject 80 tons of water into the reservoir every hour. At the same time, the reservoir supplies water to the residential area. The total amount of water supply within t hours is 802t. Now we start to inject water into the reservoir and supply water to the residential area at the same time. If the water storage in the reservoir is less than 150 tons, there will be a shortage of water supply. How many hours of water supply within 24 hours nervous?

Let the volume of water in the reservoir after X hours be y. from the meaning of the question, y = 450 + 80x-802x and T = 2x (t ≥ 0), then x = T22, ∧ y = 40t2-80t + 450 ∫ when y ≤ 150 tons, there will be water shortage, ∧ 40t2-80t + 450 ≤ 150, ∧ 2t2-4t + 15 ≤ 0, so there will be no water shortage in 24 hours