Answer:
Step-by-step explanation:
This can be set up like an inequality. Chances are just as likely that you are in ratios and proportions, but since I'm not sure, I'm going with the easier way for this particular situation. The inequality, before reducing, is:
20 < 4x < 40,
which states that a 4 minute shower uses less than 40 gallons but greater than 20 gallons, where x is the number of gallons of water. Therefore,
5 < x < 10 results when you simplify. This puts things in terms of 1 minute now. This states that a 1 minute shower uses less than 10 gallons of water but more than 5 gallons. We got this by dividing everything by 4.
Now that things are in terms of a single minute, all you have to do is multiply the greatest number of gallons by 18 and the least number of gallons by 18 (and the x as well) to get the number of gallons used in an 18 minute shower as a range:
90 < 18x < 180
