1494. In the book "An Introduction to Probability Theory and Its Applications" by W. Feller, the 1964 edition has 500 pages. What is the probability that a randomly opened page will have an ordinal number that is a multiple of 7?
Solution. From the condition of the problem, it follows that in this case, a certain event decomposes into $n=500$ equally likely cases. Of these, $m=71$ cases are favorable to the occurrence of the event of interest, since a number divisible by 7 has the form $7k$, where $k$ is an integer, and $0<7k \leqslant 500$ $\left(k \subseteq \frac{500}{7}=71 \frac{3}{7}\right)$. Therefore, the sought probability

$$
p=\frac{71}{500}=0.142
$$