Depreciation Formula?? Please!?

Depreciation varies considerable between brands of automobile.
A good general rule of thumb for new cars is 20% depreciation immediately upon purchase and 20% per year thereafter.
So a car with a new purchase price of $18,990:
Immediately upon purchase $15,192
after 1 year $12,154
after 2 years $9723
after 3 years $7778
after 4 years $6223
after 5 years $4978
after 6 years $3982
after 7 years $3186
after 8 years $2549
after 9 years $2039
after 10 years $1631
(multiply the previous figure by 0.8)

im telling u i wont survive without the game been waiting a full year;(

lets put this into context im 16 i love games (and wat everyone has a hobby gaming is mine)

they announced this game nearly a year and a half ago ive been waiting in anticipation for that long and i ve been promised this game all of a sudden i cant get this game i ll let u empathize with me here imagine u hav been waiting for this car for than a year so u can buy it all of a sudden its been delayed and u have to wait another 6 months for this car to be available but then something unfortunate happens you have no money and your parents have promised to buy u the car so u dont need to save money but then thy cant because of unforeseen circumstances this car comes out tomorrow (27th) all ur friends from skool and ur neighbours will have this car (imagine this as if they wud have the same car but with games its different ) u wud feel left out while everyones talking about their new car (or in my case a game) u wud feel torn becos u cannot get the car and u really wanted it seems unfair right?

yea well thats my situation except if u put a game there instead of a car

there are many methods for calculating depreciation. i give you some formula bellow:

1. straight line mehtod : (cost price - salvage value) / estemated life

so for your car :
depreciation per year will be : ($18990-0)/ 10 = $ 1899 [ assume that salvage value is 0]