1. A single section at a stadium can hold either 7 adults or 11 children. When $N$ sections are completely filled, an equal number of adults and children will be seated in them. What is the least possible value of $N$ ?
Answer: The least common multiple of 7 and 11 is 77 . Therefore, there must be 77 adults and 77 children. The total number of sections is $\frac{77}{7}+\frac{77}{11}=11+7=18$.