Task 5. Find the sum of the three-digit odd numbers whose digits have a product of 140.
Solution. The number $140=10 \cdot 14=2 \cdot 2 \cdot 5 \cdot 7$. It follows that the required numbers have digits 4, 5, and 7, and they are $547, 574, 745, 754$. Therefore, their sum is $547+574+745+754=2620$.

## V section - nine-year-old