Question

A water tank holds 18,000 gallons. How long will it take for the water level to reach 6000 gallons if the water is used at an average rate of 450 gallons per day?

Answer 1

If the original 18,000 gal of water is draining at a rate of 450 gal/day, we begin by calculating how many gal it needs to drain:
18,000-6,000 = 12,000 gal
Now setup 12,000 gal/1 × 1 day/450 gal, in order to cancel out gallons and have our result in days.
So 12,000/450 = 240/9 = 26.66 days, or a full 27 days rounding to the day

Answer 2

2.18,000-6,000=12,000. and then you divide 12,000 by 450 and you get 26 2/3 days.