I need to find when a phone will be worth $200 when it is currently $649.82 that depreciates in value at the rate of 63% each year.
+37158 Value = 649.82 (1-.63)^t
200 = 649.82 (1-.63)^t
200/649.82 = (.37)^t
.3077 = .37^t
log .3077 / log.37 = t=1.19 yrs 1 yr 68 days
