A store was planning to sell all of its toothpaste in 20 days at 45 units of toothpaste per day. All the toothpaste was actually sold out in 15 days. If they sold the same amount of toothpaste per day, how much more toothpaste was sold per day than they planned?
units of toothpaste
Total amount of toothpaste: 45 × 20 = 900
Amount of toothpaste each day: 900 ÷ 15 = 60
Thus, the difference: 60 - 45 = 15