Using proportions, it is found that the cost of 1 gallon of water, rounded to the nearest cent, is of $0.05.
A proportion is a fraction of a total amount, and the measures are related using a rule of three.
In this problem, we have that he uses 3.5 x 10 = 35 gallons for a 10 minute shower, which costs $1.9. Hence the cost of a gallon is of:
$1.9/35 = $0.05.
More can be learned about proportions at https://brainly.com/question/24372153
#SPJ1
