Since 5 Roberts can manufacture 5 cups in 5 seconds.
It must be that 25 Roberts should be able to manufacture 5 cups in 1 second.
Because as Roberts increase time taken to manufacture same number of cups decreases.
However we are required to find the time taken for 25 cups which is 5 times the original amount therefore it will take 5*1 sec = 5 seconds.
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This is my response to the question and may be incorrect. Feel free to rectify any mistakes