Proportions
It's assumed the amount of water consumed by one person is proportional to the time.
The contant of proportionality is given as 45 gal/day.
Since one normal year has 365 days, then we use the same proportion to calculate the water used in one year as follows:
Water used = 45 * 365 = 16,425 gallons.
The average person uses 16,425 gallons.of water in one year
