One important ratio in your career will be the nurse to patient ratio. Discuss with the class what you think the nurse to patient ratio should be in an ideal world. What do you think is a realistic figure?
State whether the ratio would vary by the category of the patients - ICU, Telemetry, Emergency, Pre-Op, Post-Op, Neonatal, etc.
Finally, assuming your realistic figure, try to estimate using proportions how many nurses would be needed in a wing with 90 patients.