## 185. Math Puzzle $10 / 80$

In Moscow, the speed of elevators in high-rise buildings is twice as fast as in ordinary buildings.

Therefore, the travel time to the 20th floor, which is at a height of $81 \mathrm{~m}$, is only five seconds longer than to the eighth floor of an ordinary building, which is at a height of $33 \mathrm{~m}$.

What are the speeds of the elevators in high-rise buildings and in ordinary buildings?
The speed of elevators in ordinary buildings in Moscow is $x$ in $\mathrm{m} / \mathrm{s}$. Then the speed of elevators in high-rise buildings is $2 x$ in $\mathrm{m} / \mathrm{s}$.

According to the problem statement, the following equation is obtained:

$$
\frac{81}{2 x}=\frac{33}{x}+5
$$

From this, $x=1.5$.

Elevators in ordinary buildings have a speed of $1.5 \mathrm{~m} / \mathrm{s}$, while the speed of elevators in high-rise buildings is $3 \mathrm{~m} / \mathrm{s}$.