Two different cars each depreciate to 60% of their respective original values. The first car depreciates at an annual rate of 10%. The second car depreciates at an annual rate of 15%. What is the approximate difference in the ages of the two cars?

Answer 1

1st car ... .60 = (1 - .10)^(t1)

2nd car ... .60 = (1 - .15)^(t2)

solve for t1 and t2

Answer 2

Let 'a' be the original value of the first car,

Let 'b' be the original value of the second car

Car A:
Final = Original(Rate)^t1
0.6a = a(0.9)^t1
0.6 = 0.9^t1
t1 = (Log0.6)/(Log0.9)
t1 = 4.85

Car B:
0.6b = b(0.85)^t2
0.6 = 0.85^t2
t2 = (Log0.6)/(Log0.85)
t2 = 3.14

t1 - t2 = 4.85 - 3.14 = 1.71

Therefore the difference in the ages of the two cars is approximately 1.7 years