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Home > CCA > Chapter 11 > Lesson 11.2.2 > Problem 11-52


The function f(x) = 140(0.7)x + 72 where x is the time in minutes, could represent the temperature over time of a hot cup of tea placed on the kitchen counter. What does the 72 represent in the context of this situation? What does the 0.7 represent? Homework Help ✎

Separate the function into its component numbers and variables:

72: Does this number seem familiar? What is special about 72°F?

x: What purpose does this number serve in the function? What does the x-axis represent?

0.7: This number gets smaller as x gets bigger. Could it represent a percentage?

200: Could this be the temperature of something? What would this be the temperature of?

72 represents room temperature.
The cup of hot tea gets continually closer to 72° as time progresses.

x represents time, probably in minutes, that has passed.

0.7 represents the 70% of heat difference that remains after each minute,
as 30% of the difference is lost.

200 represents the initial temperature of the tea.