Chapter 4 - Exponential Functions - 4.5 The Number e - Exercises and Problems for Section 4.5 - Exercises and Problems - Page 173: 17

a) $Q=500(0.93)^{t},\ 241.991$ b) $Q=500 e^{-0.07t},\ 248.293$

(a) Since the decay rate is not continuous, we have $Q=500(0.93)^t$. At $t=10$ we have $Q=500(0.93)^{10}=241.991$. (b) Since the decay rate is continuous, we have $Q=500 e^{-0.07 t}$. At $t=10$ we have $Q=500 e^{-0.07(10)}=248.293$.