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Magoosh - 数学PS - 372
Pump A can empty a pool in A minutes, and pump B can empty the same pool in B minutes. Pump A begins emptying the pool for 1 minute before pump B joins. Beginning from the time pump A starts, how many minutes will it take to empty the pool?
  • A$${A+B-1}\over{2}$$
  • B$${A(B+1)}\over{A+B}$$
  • C$${AB}\over{A+B}$$
  • D$${{AB}\over{A+B}}-1$$
  • E$${A(B-1)}\over{A+B}$$
显示答案
正确答案: B

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