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



$$6\times 54 = 324$$
$$6\times 45 = 270$$




$$5\times 64 = 320$$
$$5\times 46 = 230$$



$$4\times 56 = 224$$



$$4\times 65= 260$$



Thus the maximum is $$6\times 54 = 324$$


No comments:

Post a Comment

real analysis - How to find $lim_{hrightarrow 0}frac{sin(ha)}{h}$

How to find $\lim_{h\rightarrow 0}\frac{\sin(ha)}{h}$ without lhopital rule? I know when I use lhopital I easy get $$ \lim_{h\rightarrow 0}...