The way I usually work out questions like that is treat 3.2 as 32. Then, find two factors that make 32 (8 x 4 = 32). Divide the smallest factor (4) into 45276389 and then put 8 into the answer you get after dividing it by 4. This is simple division and multiplication to check you get the right answer. Doing it this way makes 14148871. The actual answer (done by calculator) is 14148871.5625...bingo! Practice a bit and it'll come quickly.
Edit: This method is courtesy of Bill Handley
Otherwise, stick 3 (rounded down from 3.2) into the whole lot and then minus a bit off and you'll be close.