(2) When the drug is burnt out, the concentration of the drug in the air drops, and the required time is from 6=48/x, and then x=8. Since the burning time is 8 minutes, it takes (8+8)= 16 (minutes) from the start of disinfection to entering the office.
(3) Disinfection is effective.
Because it takes y=3x/4, that is, 3=3x/4 and x=4 to reach 3 mg in the process of drug combustion, it takes 4 minutes to reach 3 mg; The time for the drug to drop to 3 mg after combustion is obtained by y=48/x, that is, 3=48/x, x= 16 (minutes). Therefore, the time from disinfection to 3 mg is (16+8)=24 (minutes).
Therefore, the time when the drug content in the air is more than 3 mg is (24-4)=20 (minutes), so disinfection is effective.
Question: In order to prevent diseases, an office is fumigated. It is known that the drug content in indoor air per cubic meter is directly proportional to time x (minutes) when drugs are burned, and after drugs are burned, Y is inversely proportional to X (as shown in Figure 17-20). Now it is measured that drugs are burned once every 8 minutes, and the drug content in indoor air per cubic meter is 6 mg.
(1) When the drug burns, the functional relationship between y and x is y=3x/4_____. The value range of independent variable x is 0.
(2) The research shows that employees can enter the office only when the drug content per cubic meter in the air is lower than 1.6 mg, so it takes at least _ 16 _ _ minutes for employees to return to the office.
(3) The research shows that the drug content in the air per cubic meter is not less than 3 mg, and the duration is not less than 10 minute, so as to effectively kill the virus in the air. Is this disinfection effective? Why?
A: Disinfection is effective.
Because it takes y=3x/4, that is, 3=3x/4 and x=4 to reach 3 mg in the process of drug combustion, it takes 4 minutes to reach 3 mg; The time for the drug to drop to 3 mg after combustion is obtained by y=48/x, that is, 3=48/x, x= 16 (minutes). Therefore, the time from disinfection to 3 mg is (16+8)=24 (minutes).
Therefore, the time when the drug content in the air is more than 3 mg is (24-4)=20 (minutes), so disinfection is effective.