Mr. Garison purchases a new freezer. Before he can store food in it, the freezer is 21C. If the temperature in the freezer decreases at a rate of 3 per hour, how long will it take the freezer to reach - 18C?

Answer:13hrs

Step-by-step explanation:

Initial Temperature = 21°c

final temperature = - 18°c

rate of decrease = 3°c/hr

for every hour the temperature decreases by 3°c.

What time does it take to get to 0c =. 21 (°c) / 3 (°c/hr) =. 7hr

what time does it take to get to - 18c = 18 (°c) / 3 (°c/hr) =. 6hr

Total Time taken =. 7hr + 6hr = 13hr

Alternative solution

Initial Temperature = 21°c

final temperature = - 18°c

rate of decrease = 3°c/hr

(21 + 18) °c / 3 (°c/hr). =. 13hr