it would be 3 21/100 because 3 is the whole number, and .21 is twenty one hundredth. so if the question had said "write 1.60 as a proper fraction," then it would be 1 60/100. however you still would not be done. if you are able to simplify the fraction, then you should. so the answer for 1.60 would be 1 6/10, then 1 3/5.