Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 28 hours. If one additional machine were used under the same operating conditions, in how manyfewerhours of simultaneous operation could the production order be fulfilled?
Choose the most appropriate option
A) 7 B) 9 C) 12 D) 27 E) 48
If 3 Machines can do the work in 28 hr then 4 Machines can do the work in   3/4*28= 
<gadget id="calculator">  3/4*28</gadget>
<output>21</output>
21 Hrs. hence time saved will be 7hr   option 7 is the correct answer
<result>A</result>
Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 28 hours. If one additional machine were used under the same operating conditions, in how manyfewerhours of simultaneous operation could the production order be fulfilled?