There are several information's that are given in the question. Based on those given information's the answer can be easily deduced.
Number of cups that a coffee pot makes in 1 1/2 minutes = 6 cups
Number of cups that a coffee pot makes in 3/2 minutes = 6 cups
Then
Number of cups that a coffee pot makes in 1 minute = 6/(3/2) cups
= 12/3 cups
= 4 cups.
I hope that the procedure is clear enough for you to understand.