62. There were books on three shelves. On the bottom shelf, there were 2 times fewer books than on the other two, on the middle shelf - 3 times fewer than on the other two, and on the top shelf - 30 books. How many books are there in total on the three shelves?
62. Let the number of books on the lower shelf be 1, then the number of books on the two other shelves will be 2 units, and on the three shelves - 3 units. This means the number of books on the lower shelf is $\frac{1}{3}$ of all the books. Similarly, the number of books on the middle shelf is $\frac{1}{4}$ of all the books. Therefore, the number of books on the upper shelf will be $1-\left(\frac{1}{3}+\frac{1}{4}\right)=\frac{5}{12}$, or 30 books. Thus, the total number of books is $30: \frac{5}{12}=72$.