Step 1 :Given the function \(C(t)=7+17 e^{-0.038 t}\), where \(C(t)\) is the temperature of the water in degrees Celsius and \(t\) is the number of minutes since the bottle was placed in the cooler.
Step 2 :We need to find the time \(t\) when the temperature \(C(t)\) reaches 20 degrees Celsius. So we set \(C(t) = 20\) and solve for \(t\).
Step 3 :Subtract 7 from both sides of the equation to get \(17 e^{-0.038 t} = 13\).
Step 4 :Divide both sides of the equation by 17 to get \(e^{-0.038 t} = \frac{13}{17}\).
Step 5 :Take the natural logarithm of both sides to get \(-0.038 t = \ln\left(\frac{13}{17}\right)\).
Step 6 :Finally, divide both sides by -0.038 to solve for \(t\).
Step 7 :By calculating, we find that \(t\) is approximately 7.1.
Step 8 :So, Dan should leave the bottle in the cooler for approximately \(\boxed{7.1}\) minutes.