The food starts at 25^ extoC and cools at 6^ extoC per hour until it reaches the freezer temperature of -8^ extoC. What is the temperature of the food after 10 hours and after 7 hours?

Since the food cannot cool below the freezer temperature of $-8^\circ C$, if the given time is greater than 5.5 hours, the temperature will be $-8^\circ C$.

a) 10 hours

Since $10 \text{ hours} > 5.5 \text{ hours}$, the food will have already reached the freezer temperature.
The temperature of the food after 10 hours will be $\boxed{\mathbf{-8^\circ C}}$.

b) 7 hours

Since $7 \text{ hours} > 5.5 \text{ hours}$, the food will have already reached the freezer temperature.
The temperature of the food after 7 hours will be $\boxed{\mathbf{-8^\circ C}}$.

QUESTION 5

a) After a dry season, the river level is $-3$ metres. How many metres would the river need to rise to reach flood level?

Calculate the difference.

b) If the level rose from $-3$ m to $-2$ m, how much did it rise?

c) In the rainy season, the level rose from $-2$ m to 1.5 m. By how much did it rise?

d) When some of the water had drained away, the depth fell from 1.5 m to $-0.6$ m. By how many metres had it fallen?