Twelve machines, each working at the same constant rate, together can complete a certain job in 6 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 3 days?	Answers:
A) 14	B) 12	C) 15	D) 16	E) 18
Rate of one machine = 1 job / (12*6) days   let X = number of machines needed to complete the job in 3 days   1/(12*6) * 3 * X = 1 job   X = 24   24-12= 
<gadget id="calculator">24-12</gadget>
<output>12</output>
12   ANSWER: 12
<result>B</result>
Twelve machines, each working at the same constant rate, together can complete a certain job in 6 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 3 days?