To improve her health, Mary decides to drink 1.5 liters of water a day as recommended by her doctor. Mary's glasses hold 250 mL of water. How many glasses of water should Mary drink per day to reach her goal? Let's be accurate as possible.
Each liter of water holds 1000 mL. Mary's goal is to drink 1.5 liters of water a day, which in mL is 1.5 L * 1000 mL / L = 1500 mL. To reach her goal, Mary should drink 1500 mL / 250 mL / glass = 6 glasses of water per day.
The answer: 6.