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Question
by papergangsta » Sun Nov 07, 2010 3:27 pm
Is there a trick to multiplying numbers in the form ab x ba? Like 47 x 74?
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Re: Question
by shrig94 » Sun Nov 07, 2010 6:45 pm
(10a+b)*(10b+a)=100ab+10(a^2+b^2)+ab
Though, that is probably slower than foiling.
Though, that is probably slower than foiling.
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M-348
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M-348
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CS-160
Shri, AAA, Hirschi
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Re: Question
by AuSmith » Mon Nov 08, 2010 11:48 am
Yea, it's a matter of personal preference. The best trick if there is one is probably to multiply the product of the digits by 101 and add ten times the squares of the digits...
Ex. 47*74
4*7=28, so you have 2828 so far.
then we add 16+49=65 and multiply it by 10...
2828+650=3478
That's about it...
Ex. 47*74
4*7=28, so you have 2828 so far.
then we add 16+49=65 and multiply it by 10...
2828+650=3478
That's about it...
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