Posted on 08/11/2009 7:48:27 AM PDT by rawhide
Interesting. Does this work only with numbers ending in 5?
How about 95x95?
I also multiplied 87x36 using your formula, and I cannot get it to come out to the correct number?
And the two guys who paid you 33 bucks.
That’s cool!
“Much to his dismay, he’s about to discover that copyright protects the expression but not the idea...”
Except in software patents, which do protect the idea, which is why they are such a disgrace.
It’s like copyrighting the idea of boy meets girl, boy loses girl, boy gets girl, and then charging a license fee to every fiction writer who uses that plot line. DISGRACEFUL.
jas3
I couldn’t tell from your example how you picked the multiplier for the first digits.
1x2, 4x5... How do you know the multiplier for the first digits?
Also didn’t follow the example for using it for other numbers.
Or (1000*2009) - 2009 = 2006991
Secrets of Mental Math: The Mathemagician's Guide to Lightning Calculation and Amazing Math Tricks
1st digit is 6. Add 1 to one of the digits. 1+6=7. Then multiply that times the second first digit so you get 6X7=42. 5X5=25.
Answer to 65X65=4225.
905X905=819025! 90X90=8100. Add 90 to sum and get 8190. Add 25, (5X5) and you get the answer 819025! excel or cell phone is easier!
I am no good at multiplication. But I can add four 4 digit numbers in the neighborhood of 1 second.
I don’t know. You can probably describe it algebraically. The key to schemes like this is more about utilizing the capacity of human memory than any particular trick.
It’s kind of sad because it isn’t worth $33 these days. I bought a free iPhone app that’s even faster.
I can measure marigolds without the use of an inchworm, and will tell you how for $32.95
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