In 1991, the cost of mailing a 1 oz. first-class letter was 29 cents, and the inflation rate was 4.6%. If the inflation rate stayed constant, the function C(t) = .29(1.046)t would represent the cost of mailing a first-class letter as a function of years since 1991.
Question: In 2007, the cost of mailing a first-class letter was 41 cents. Has the inflation rate stayed constant since 1991? Explain.

Question

In 1991, the cost of mailing a 1 oz. first-class letter was 29 cents, and the inflation rate was 4.6%. If the inflation rate stayed constant, the function C(t) = .29(1.046)t would represent the cost of mailing a first-class letter as a function of years since 1991.
Question: In 2007, the cost of mailing a first-class letter was 41 cents. Has the inflation rate stayed constant since 1991? Explain.

mathstudent55 · Answer

You mean C(t) = 0.29(1.046)^t, right? t is an exponent, isn't it?
If so, then 
t = years since 1991, so 2007 - 1991 = 16
C(16) = 0.29(1.046)^16 = 0.60
Answer is no.

anonymous · Answer

yes it is an exponent :) thank you so so much!! @mathstudent55

anonymous · Answer

do you know this question having to do with the same problem? 1.	If the function given holds true, in what year would the cost of mailing a first-class letter reach 60 cents?  @mathstudent55

anonymous · Answer

:)

mathstudent55 · Answer

When we let t = 16, which represents 1991 + 16 = the year 2007, we did get C = 0.60, so the answer is 2007.