1. The problem is to convert 90,000 centigrams (cg) to grams (g). 2. We know the conversion factor: 1 gram = 100 centigrams. 3. To convert centigrams to grams, we multiply by the fraction $\frac{1\text{ g}}{100\text{ cg}}$ because this equals 1 and changes units from cg to g. 4. The correct expression is: $$90,000\text{ cg} \times \frac{1\text{ g}}{100\text{ cg}}$$ 5. Simplifying, the centigrams units cancel out: $$= 90,000 \times \frac{1}{100} \text{ g} = 900 \text{ g}$$ 6. Therefore, the correct expression to convert 90,000 cg to grams is: $$90,000\text{ cg} \times \frac{1\text{ g}}{100\text{ cg}}$$