Final answer:
The average change in the creek's water level after a flood is -4/5 foot per hour. This is calculated by dividing the total change of -2 4/5 feet by the period of 3 1/2 hours.
Step-by-step explanation:
The student is asking about the average change in water level per hour after a flood. To calculate this, we take the total change in water level, which is -2 4/5 feet, and divide it by the total time, which is 3 1/2 hours. The negative sign indicates that the water level is decreasing.
First, we convert the mixed numbers to improper fractions. For the change in water level, -2 4/5 becomes -14/5 feet. For the time, 3 1/2 becomes 7/2 hours.
Next, we divide -14/5 feet by 7/2 hours to find the average change per hour. To do this, we multiply by the reciprocal of the divisor: -14/5 × 2/7. Simplifying, we find that the average change in water level is -4/5 foot per hour.