Mathematics

Problem

A cup of tea cools from

90^\circ\text{C}

t=0

minutes to

70^\circ\text{C}

t=5

minutes. Determine the average rate of change of temperature over this time interval, including the correct sign and units. a)

4^\circ\text{C}

per minute b)

-20^\circ\text{C}

per minute c)

-4^\circ\text{C}

per minute d)

-0.25^\circ\text{C}

per minute