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The answer to the exercises in the second volume of the eighth grade mathematics book taught by scholars is 17.438+0.
1, the degree y (degree) of myopia in life is inversely proportional to the focal length x (meter) of the lens. Given that the focal length of a 400-degree myopia lens is 0.25m, then y=x/ 100.

2. no.

3. The functional relationship between m and n: m=n/ 100.

If the average daily electricity consumption is 4 degrees, that is, n=4, then m=4/ 100=250 (days).

4. Fill in the first line in turn: 4,3/10,2,13/20,4/5,9/10;

Fill in the second line in turn: 100, 50, 3/ 100, 25.

6、⑴t=u/ 1200

(2) According to the meaning of the question, 60 employees can put up to 300 tons of rice every day, that is, u=300 tons/day. If n/ 1200 is substituted, t=300/ 1200=4 (days).

(3) According to the meaning of the question, the corn left by employees after two days of continuous work is 1200-2×300=600 tons.

Suppose x people are needed to complete the task. 60/300×(60+x)=600 x=60。

7、⑴a=b/70

(2) meaningful; Xiao Wang has consumed oil since he arrived in the county: 300×0. 1=30 liters, and there is still oil in the tank; 70-30=40 liters, and the oil required for the return trip: 300×0.2=60 liters > 40 liters, and 60 liters -40 liters =20 liters.

So the oil in the tank is not enough to return to the county seat, and at least 20 liters of oil is needed.