Step 1 :The temperature $T$ of an object in degrees Fahrenheit after $t$ minutes is represented by the equation $T(t)=66 e^{-0.017t} +73$.
Step 2 :We are asked to find the temperature of the object after one and a half hours. Since 1.5 hours is 90 minutes, we substitute $t$ with 90 in the given equation.
Step 3 :Substituting $t$ with 90, we get $T = 66 e^{-0.017*90} +73$.
Step 4 :Calculating the above expression, we get $T = 87.29135404285647$.
Step 5 :Rounding to the nearest degree, we get $T = 87$.
Step 6 :Final Answer: The temperature of the object after one and a half hours is approximately \(\boxed{87}\) degrees Fahrenheit.