You might fear that a '2' or higher digit might move into the one's place. Try this: multiply the biggest decimal fraction 0.99999... by two. This yields 1.99999... Even with this fraction a '1' moves into the one's place.
Here is an table set up to convert 0.75 to binary. Fill in the table by typing numbers in the boxes. Or, do the work with pencil-and-paper.
Perform the conversion.