Five identical machines working independently complete a production run in 18 minutes. How many minutes would 15 such machines need for the same run? Enter the number of minutes.
Correct answer
6
Explanation
The run requires 5 times 18, or 90 machine-minutes, so 15 machines need 90 divided by 15, which is 6 minutes. Multiplying 18 by 3 to get 54 follows direct proportion and reverses the expected effect of using more machines.