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