其它
The students of a class can be divided into groups of $5$ or groups of $7$ when there is a groupwork to do. How many students at least are in that class? 
Overseas Competition->Knowledge Point->Number Theory Modules->Factors and Multiples->Common Factors and Common Multiples->Common Multiples and Least Common Multiples->Least Common Multiple of Two Numbers
The least common multiple of $5$ and $7$ is $35$. 