Question 714886
Finding these facts will help you:

{{{4=2^2}}}
{{{5=5^1}}}
{{{6=2^1*3^1}}}
{{{9=3^2}}}
{{{28=2^2*7^1}}}


Look at all the prime number factors involved in the set of numbers listed.  You need to use each prime factor the greatest number of times that it is present in the list.  THAT gives the product you are looking for.


prime-----------highest expon
2?----------------2
3?----------------2
5?----------------1
7?----------------1

I left the last couple of steps undone.