8 identical machines, working alone and at their constant rates, take 6 hours to complete a job lot. How long would it take for 12 such machines to perform the same job?
Choose the correct choice
A) 6 hours	B) 8.75 hours	C) 12 hours	D) 4 hours	E) 16 hours

Rationale: "let each machine do 1 unit of work for 1 hour 8 machines - - > 8 units of work in 1 hour for 6 hours = 8 * 6 = 48 units of total work is done . now this 48 units of total work must be done by 3 machines 12 units of work ( 12 machines ) - - - > 1 hour for 48 units of work 12 * 4 - - - > 1 * 4 hours d 4 hours"
Answer: D