water footprint

Question

1. A family of three would like to reduce their water footprint so that it is 75% of the typical American’s water footprint. Which calculation shows how they can estimate their target water footprint for one day? There may be more than one correct answer.
2. 2,500×3×0.75
3. 2,500÷(365×0.75)×3
4. (3×2,500×34)÷365
5. 3×(2,500×0.75)÷365
6. 2,500×3×43÷365
7. 2,500×3÷0.75
8. 3×2,500×0.75÷365
9. 
   

Answer 1

Hello Kaitlyn, this is an excellent question. I looked up the figure on google and an article from the University of Florida came up that says the average individual's water footprint in the US is 1,802 gallons/day (or 6,821 L/day).

So if each family member was trying to estimate their target daily water footprint it would be 1,802 gallons multiplied by something to get their individual target. The question says they want to be less than 75% less than the average water footprint. So first you have to convert 75% into its decimal form, which we do by dividing by 100 [or moving the decimal two places to the left]. Thus 75% = 0.75 in decimal form.

To get each family member's target we multiply our reference value (1,802) by the portion they want to be under (0.75).

1,802 * 0.75 = 1,351.5 gallons/day.

If we want the family's total target, we just have to multiply that by 3.

(1,802 * 0.75) * 3 = 4,054.5 gallons/day.

I only see one answer choice that fits that pattern. Now, I'm ASSUMING that is what the question is asking because the phrase '75% of the typical American's footprint' taken literally would mean 2 things:

1. That the figure isn't 1,802 gallons/day because America includes all of North and South America, so it would likely be the mean or median of every individual in North and South America, but more importantly
2. it would mean the family of 3 was attempting to lower their combined water footprint to below 75% of a single American individual. So in that case the setup would look a little different:

(1,802 gallons/day * 0.75) = 1351.5 gallons/day ÷ 3 = 450.5 gallons per person per day.