Question

1. a coffee shop uses 4 liters of milk every day.

a. if there are 15 liters of milk in the refrigerator, after how many days will more milk need to be purchased? explain how you know.
b. if only half as much milk is used each day, after how many days will more milk need to be purchased?

Explanation:

Step1: Calculate daily milk use (part b)

New daily use: $\frac{4}{2}=2$ liters

Step2: Find full days milk lasts

Divide total milk by new daily use: $\frac{15}{2}=7.5$

Step3: Interpret the result

After 7 days, $7\times2=14$ liters are used, leaving 1 liter. On day 8, more milk is needed.

Answer:

Part a:

After 3 days, more milk will need to be purchased. In 3 days, the shop uses $3\times4=12$ liters, leaving $15-12=3$ liters, which is not enough for the 4th day's usage.

Part b:

After 7 days, more milk will need to be purchased.