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Question: Which answer is correct?

I tried to calculate n = 1.65(2.5)\(.25) and it invariably gives me 33\2. I ask it to approximate and it gives me either 66 or 16.5. On several occasions, I have recieved the answer 74,121. Why does this happen? I'm guessing that it might have something to do with the way which I originally entered the equation; but if so what is the "correct" way to enter it?