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?

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

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