Answer:
b) 9
Step-by-step explanation:
Given: Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in hours.
To Find: If one additional machine were used under the same operating conditions, in how many fewer hours of simultaneous operation could the production order be filled.
Solution:
Let the time taken by one machine to fill a certain production alone be
Time taken when three machine operate independently and simultaneously
Let time taken when one additional machine is used
Time when when one additional machine is used
it takes when one additional machine is used
Now,
fewer hours taken when one additional machine is used
in fewer hours of simultaneous operation the production order can be filled if one additional machine is used
Hence option b) is correct.