想請問一下這題如何算? 謝謝!
191. Pumps A,B,and C operate at their respective constant rates. Pumps A and B, operating simultaneously, can fill a certain tank in 6/5 hours; pumps A and C, operating simultaneously, can fill the tank in 3/2 hours; and pumps B and C, operating simultaneously, can fill the tank in 2 hours. How many hours does it take pumps A,B, and C, operating simultaneously, to fill the tank?
(A)1/3
(B)1/2
(C)2/3
(D)5/6
(E)1
正確答案是(E)