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3. maree has recently purchased a new chest deep freezer for...

Question: maree has recently purchased a new chest deep freezer for...

Question details

Maree has recently purchased a new chest (deep) freezer for keeping food at the very low temperature

of –18°C.

Maree is interested in determining how long it will take some foods to freeze and how long it will

take some foods to thaw.

a Maree understands that her new freezer can lower the temperature of food at a rate of 6°C per hour.

Maree places some food, currently at a room temperature of 24°C in her new freezer. How long

will it take for the food to reach the freezer temperature of –18°C?

b On a different day, Maree discovered that a loaf of bread only took four hours to freeze to the

temperature of –18°C. What was the room temperature on this day?

c Maree wishes to determine the rate at which frozen meat can thaw and return to a temperature of

5°C ready for her to cook. She carries out the following test cases:

(Note the below is a table, columns separated with / sign)

Size of frozen meat /Room temperature/ Time to reach 5°C

3 kilograms/ 12°C/ 4 hours

1 kilogram/ 16°C/ 55 minutes

2 kilograms/ 10°C/ 2 hours and 20 minutes

1 kilogram/ 22°C/ 40 minutes

Based on Maree’s test cases, what is an average time for how long it takes food to thaw (and reach

5°C) per kilogram of frozen meat for a normal room temperature of 15°C?

d If Maree has a 4 kg frozen turkey in the freezer that she wishes to start cooking at 4:30 p.m., and

she estimates the average room temperature during the day will be 19°C, what time would you

suggest Maree takes the turkey out of the freezer?

e If Maree has an n kg frozen piece of meat that she wishes to cook in t hours and the room

temperature is 15°C, when should Maree take the meat out of the freezer? Your answer will be an

expression in terms of t and n.