Question

The price for US postage stamps has increased over the years. Since 1975, the price has increased from $.13-$.37 in 2005 at a rate that is approximately linear.
Write a linear model for the price of stamps during this time. Let P represent the price and T represent the number of years since 1975.


What would you expect the price of a stamp to be in 2015?









(Please show your work)

Answer 1

Answer:

Linear Equation: P = 0.008T + 0.13

Price of stamp in 2015 = $0.45

Step-by-step explanation:

From 1975 to 2005 [30 years], the price increased from 0.13 to 0.37 [0.24].

This means the rate of change (slope) is 0.24/30 = 0.008

This means Price changed (increased) by $0.008 per year.

Slope = 0.008

The y-intercept (P) is at the starting point which is at T = 1975, the price was 0.13. Hence y-intercept is 0.13

The equation of a line is given as

P = mT + b

Where m is the slope and b is the y-intercept

Now, we can write the linear model equation as:

P = 0.008T + 0.13

To find the price of stamp in 2015, we see that this is 40 years later after 1975. So we plug in 40 into T in the equation found above:

P = 0.008(40) + 0.13

P = $0.45