Final answer:
The family's rate of water usage per day is 9.1 gallons, which is significantly lower than the national average of 125 gallons per household per day. The calculation straightforwardly uses the provided daily usage figure, and additional context from the national averages can provide insights into water consumption habits.
Step-by-step explanation:
The question concerns the rate of water usage per day by a family. To calculate this, we will use the information provided that the family uses 9.1 gallons of water each day. This figure itself represents the family's rate of water usage per day. In comparison to other statistics, the average American family's daily indoor water use is about 125 gallons, making this family's usage significantly lower than the national average.
When the family's usage is scaled up to include more people, as in the provided information—a total of 91 gallons for two people is about 45 gallons per person—it can be calculated in terms of energy equivalent (kWh/day) and compared to the national average. To consider the environmental impact, one can refer to the water footprint which takes into account both the use and location of water consumption.
Using similar calculations as in the examples provided, we can compare this family's rate of water usage with other households or national averages to gain insight into their water consumption habits and potential areas for improvement or conservation.