Answer
The probability that the food is digested in less than 30 minutes
is $\approx0.3935.$
Work Step by Step
The exponential density with mean 1 is $e^{-x}$
The probability that the food is digested in less than 30 minutes
is $ \int\limits_{0}^{\frac{1}{2}} e^{-x} dX = -e^{\frac{-1}{2}}+1\approx 0.3935$
