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190310
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The swimming pool will be filled with water whose rate of flow is 50 L/min. The pool is 120 m^3 in total. How many hours is necessary to fill 2/3 of the pool?
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190310
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$$B_n=A_{n+1}-A_{n},B_{n+1}-B_{n}=2$$.$$A_{10}$$=?
1: $$A_1=1,A_3=3$$
2: $$A_2=2,A_4=4$$
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190310
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The cuboid of 24*20*10 inch^3 is coated with a 1 inch plastic foam. How many cubic feet is the difference between the volume of the cuboid before and after coating the plastic foam?
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190310
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$$\frac{1}{(2n-1)!} - \frac{1}{(2n+1)!} = \frac{an^2+bn+c}{(2n+1)!}$$.a+b+c=?
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190310
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$$ax^2+bx+c=0$$ Does the equation have at least one solution?
1:a > 0
2:c < 0
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190310
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r,s,t are positive integers. t=?
1:s=rt+s
2:st=r
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190310 还原机经选题
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If the 40 consecutive positive integers 1-40 are divided by 6 to get 40 residues, what is the sum of the residues?
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