Question 206354
Basically,  we  are  asked  to  pick  two  3 digit  numbers,  which  when  multiplied  together  are  a  max  for  this  set.
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if  we  try  to  maximize  the  hundreds  digit:
100*200=20,000
300*400=120,000
500*600=300,000,,this  suggests  that  the  hundreds  digits  are  5 &6
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working  on  the  10's  digit:
610*520=317,200
620*510=316,200
630*540=340,200,,,,,,max,,,lets  use these
640*530=339,200 
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working  on  the  tens  digits:
631*542=342,002,,,,,,max,,,,,answer
632*541=341,912
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Therefore  using  only  the  digits  1 to 6, and  each  only  once, 
the  max  product is  342,002,  from  631*542
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