Jonas purchased a new car for $15,000. Each year the value of the car depreciates by 30% of its value the previous year. In how many years will the car be worth $500?
+3693 How I did it was like a percent formula.
30% of 15,000 is 4,500. Then I would subtract 4,500 from 15,000 to get 10,500. Then i would repeat the process over again. (30% of 10500 and then subtract).
However, I would like to comment on how complex and very accurate your calculations are! They are spot on! Nice job, Chris! 
+3693 I think it would be inbetween 9-10 years, because in the 9th year, the car is worth $603.30, while in the 10th year, the can is only worth $422.31.
+128732 Check out the big brain on BJ !!!
She is correct...it IS betwen 9 and 10 years
Let's see if we can narrow it down a little more.....
500 = 15000(.7)^t where t is the time to depreciate to $500 ....divide both sides by 15000
1/30 = .7^t take the log of both sides
log (1/30) = log.7 ^t and we can write
log(1/30) = t * log .7 divide both sides by log.7 and we have
log(1/30) / log. 7 = t = about 9.5 years......
+3693 How I did it was like a percent formula.
30% of 15,000 is 4,500. Then I would subtract 4,500 from 15,000 to get 10,500. Then i would repeat the process over again. (30% of 10500 and then subtract).
However, I would like to comment on how complex and very accurate your calculations are! They are spot on! Nice job, Chris!
