Saturday, 20 September 2014

arithmetic - Exercise: Construct two numbers using figures 4,5 and 6 whose product is as big as possible



Precisely what it says in the title.



Construct two numbers using figures 4,5 and 6 whose product is as big as possible.




I don't know whether I can use a same number again (4456, f.e.) or only 4,5 and 6 (I'm guessing it's this one).



I could go about it with trial and error, but would like to know the reasoning behind it.



PS: I thought about 654 * 645 because the bigger the number in the place of the hundreds, the bigger the result.


Answer



There are only 6 choices, namely



6×54=324
6×45=270




5×64=320
5×46=230



4×56=224



4×65=260



Thus the maximum is 6×54=324


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