1. **State the problem:** Harley needs to cut the grass on a rectangular field that is 100 meters long and 90 meters wide. She cuts grass at a rate of 30 square meters per minute. We need to find how many minutes it will take her to cut the entire field. 2. **Formula for area of a rectangle:** The area $A$ of a rectangle is given by: $$A = \text{length} \times \text{width}$$ 3. **Calculate the area of the field:** $$A = 100 \times 90 = 9000 \text{ square meters}$$ 4. **Calculate the time to cut the grass:** Since Harley cuts 30 square meters per minute, the time $t$ in minutes is: $$t = \frac{\text{total area}}{\text{cutting rate}} = \frac{9000}{30}$$ 5. **Simplify the expression:** $$t = 300 \text{ minutes}$$ **Answer:** It will take Harley 300 minutes to cut all the grass on the field.