2. (10 points) When the escalator is not operating, it takes a child 90 seconds to walk the entire 60 meters of the escalator. When the escalator is operating, it takes 60 seconds to transport passengers from the bottom to the top. If the child walks on the operating escalator, how many seconds will it take for the child to reach the top from the bottom of the escalator? $\qquad$seconds.
【Analysis】If we consider the length of the escalator as a unit "1", then the time it takes for the child to walk the 60 meters long escalator is $\frac{1}{90}$, and the time it takes for the escalator to transport passengers from the bottom to the top is $\frac{1}{60}$. Therefore, the time it takes for the child to reach the top from the bottom of the escalator is $1 \div\left(\frac{1}{90}+\frac{1}{60}\right)$, solving the problem.
【Solution】Solve: $1 \div\left(\frac{1}{90}+\frac{1}{60}\right)$
$$
\begin{array}{l}
=1 \div \frac{1}{36} \\
=36 \text { (seconds) }
\end{array}
$$

Answer: It takes the child 36 seconds to reach the top from the bottom of the escalator.
Therefore, the answer is: 36.