Machine A can finish a job in 6 hours, Machine В can finish the job in 12 hours, and Machine С can finish the job in 8 hours. How many hours will it take for A, B, and С together to finish the job?  Answers: A) 6/5 B) 7/4 C) 8/3 D) 9/2 E) 12/5
The combined rate is 1/6+1/12+1/8 = 9/24 of the job per hour.   The time to complete the job is 24/9 = 8/3 hours.   The answer is 8/3.
<result>C</result>
Machine A can finish a job in 6 hours, Machine В can finish the job in 12 hours, and Machine С can finish the job in 8 hours. How many hours will it take for A, B, and С together to finish the job?