[問題]GWD12-30

[luluhsiao]

GWD12-30
Q30:
Machine A, operating alone at its constant rate, produces 500 feet of a particular fiber in 2 hours. Machine B, operating alone at its constant rate, produces 500 feet of the same fiber in 3 hours. Machine C, operating alone at its constant rate, produces 500 feet of the same fiber in 5 hours. How many hours will it take machines A, B, and C, operating together at their respective constant rates, to produce 1,000 feet of the fiber?

Ans : (A) 60/31

麻煩了....

[nicoleliu]

A--> 250 f/ hr
B--> (500/3) f/hr
C--> 100 f/hr

A+B+C together 一小時可做=250+(500/3)+100=1550/3 feet

總共1000 feet, 所需時間=1000 / (1550/3)=60/31 hr

[luluhsiao]

喔...原來就這樣呀...謝謝..