If 285 million gallons of water were treated in a month and 200,000 gallons of backwash water was used per day, what percentage of backwash water was used?

To determine the percentage of backwash water used in relation to the total amount of water treated, first, we calculate the total volume of backwash water used throughout the month.

Given that 200,000 gallons of backwash water is used per day, we can find out how much is used in a 30-day month. The calculation would be as follows:

200,000 gallons/day * 30 days = 6,000,000 gallons of backwash water used in the month.

Next, we need to find the percentage of backwash water used out of the total treated water. The total treated water is 285 million gallons, which can also be expressed as 285,000,000 gallons.

The percentage of backwash water used is calculated by taking the total backwash water used and dividing it by the total treated water, and then multiplying by 100 to obtain a percentage:

(6,000,000 gallons backwash / 285,000,000 gallons treated) * 100.

This equals:

(6,000,000 / 285,000,000) * 100 ≈ 2.1%.

Thus, the answer is approximately 2.1%, which corresponds to the choice stating that about