The product of any $$3$$-digit whole number and any $$2$$-digit whole number can contain at most how many digits? 
Overseas Competition->Knowledge Point->Number Theory Modules->Place Value and Number Bases->Numbers
The largest product of a $$3$$-digit number and a $$2$$-digit number is $$999\times99 = 98901$$. That product has $$5$$ digits. 