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
lvoyster
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.

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