At Rosemont Middle School, \( 55 \% \) of the student body purchases their lunch at school. 1. Write that as a ratio of part to whole.

To write \( 55\% \) as a ratio of part to whole, we can express it as a fraction. The percentage \( 55\% \) means \( 55 \) out of \( 100 \). Therefore, the ratio of students who purchase lunch to the total student body is \( 55:100 \). This ratio can be simplified by dividing both numbers by their greatest common divisor, which in this case is \( 5 \). Thus, the simplified ratio becomes \( 11:20 \).