Avril likes collecting baseball cards. The number of cards she has is divisible by $$2$$, $$3$$, and $$5$$. How many baseball cards does Avril have at least? 
Overseas Competition->Knowledge Point->Number Theory Modules->Factors and Multiples->Common Factors and Common Multiples
The total number of baseball cards is the least common multiple of $$2$$, $$3$$, and $$5$$, i.e. $$\left[ 2,3,5\right]=2\times3\times5=30$$. 