If the price of a car will triple every 4 years, write an equation to model the price after x four year periods and how long did it take for the price to go from $180,000 to $4,860,000?

1 Answer
Apr 29, 2018

y=3^xP where x is the number of four-year periods.

Explanation:

The car starts at a price of P.
After 4 years, (1 four-year period) it will cost 3P=3^1P.
After 8 years (2 four-year periods) it will cost 3(3P)= 3^2P
After 12 years (3 four-year periods) it will cost 3(3^2P)= 3^3P
The pattern is y=3^xP.

You need to solve the equation

3^x*180,000=4,860,000
3^x=27=3^3
x = 3 four-year periods
So it took 12 years.