standard_description: Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).
problem_activity: Task
A cup of hot coffee will, over time, cool down to room temperature.  The
principle of physics governing the process is Newton's Law of Cooling.
Experiments with a covered cup of coffee show that the temperature (in
degrees Fahrenheit) of the coffee can be modelled by the following
equation
$$
f(t) =  110e^{-0.08t}+75.
$$
Here the time $t$ is measured in minutes after the coffee was poured into
the cup.
Explain, using the structure of the expression $110e^{-0.08t} + 75$,
why the coffee temperature decreases as time elapses.
What is the temperature of the coffee at the beginning of the experiment?
After how many minutes is the coffee $140$ degrees?
After how many minutes is the coffee $100$ degrees?


aligns: no