Exponential decay

Question

Suppose that a phone that originally sold for $800, loses a fraction of its value each year after it is released. An equation to represent value, version of the phone, T years after it released is V equals parentheses( 2/5) X.

what would the value be in dollars at year one, two, three, and year four?

Answer 1

800(2/5)^x

800(2/5)^1

= 1600/5= $320 after one year

800(2/5)^2

=3200/25 = $128 after 2 years

800(2/5)^3

=6400/125 = $51.20 after 3 years

800(2/5)^4

=12800/625=$20.48 after 4 years