Question

A cellphone worth P15,000 was bought 5 years ago. If it depreciates 5% per annum, how much does it cost now?

Answer 1

$$C(t)=P(1-r/n)^{n(t)}$$

$$C(5)=15000(1-0.05/1)^{1(5)}=11606.71$$

It costs P11606.71 now.