You buy a computer for $1200. The value of the computer decreases by 30% each year. Find the value of the computer after 4 years.
Please show work! Thanks!

Question

You buy a computer for $1200. The value of the computer decreases by 30%  each year. Find the value of the computer after 4 years.
Please show work! Thanks!

anonymous · Answer

Let c = value of computer in dollars.  Let t= the number of years

$$c=1200e ^{-.3t}$$$$c=1200e ^{-.3(4)}$$

c= $361.43

anonymous · Answer

Thanks the only thing is that my teacher got the answer: $288.12

anonymous · Answer

Sometimes he is wrong though...

anonymous · Answer

He probably using a linear equation instead of an exponential.

Have you discussed logarithms?

anonymous · Answer

We did logarithms about 2 months ago.

anonymous · Answer

Check back a little while and I'll see if I can come up with the linear equation

anonymous · Answer

okay you can take your time :) really, thanks for helping me. It does mean a lot. :)

anonymous · Answer

It's not a linear equation, but an exponential equation.

$$c=1200(.7)^{t}$$

So for t=4 years

$$c=1200(.7)^{4}$$ Which gives us $288.12

The difference between the first equation I wrote and the new one is that in the first one the computer lost value continuously.

anonymous · Answer

Thank you so much!!! ^_^