2010-06-20
Original: 2010-06-20 on Saturday Morning Breakfast Cereal
Transcript
Title: It's called "Polish hand magic."*
One palm is worth 5.
Now, say you multiply 7x8.
2 + 3 fingers up = 5
3 x 2 fingers down = 6
And there's the answer: 56
Narrator: It works for bigger or smaller numbers. Just imagine negative fingers and extra fingers.
Flame-haired character (excited): I'm so powerful.
Flame-haired character: Is this you right now? Why?!
Narrator: See if you can figure it out before moving on.
Here's the proof:
10[(x-5)+(y-5)] + 1[(10-x)*(10-y)]
(labeled: 10 times sum of up values) + (labeled: 1 times product of down values)
= 10x + 10y - 10x - 10y + x*y
= x*y
Narrator: Now that you've seen the proof, you know fully why it works.
Flame-haired character: But... why?
Flame-haired character: Right, but how?
Flame-haired character (distressed, staring at "x*y"): It still seems like magic.
Narrator: This is the worst thing about being human.
*Source: The Puzzler's Elusion, by Dr. Dennis Shasha, who apparently got it from "a smart and elegant Polish woman."
Votey:
Caption: Me, all day Friday:
Bearded man (hand on chin, amazed): This is the coolest thing ever! Someone needs to inform the President!
One palm is worth 5.
Now, say you multiply 7x8.
2 + 3 fingers up = 5
3 x 2 fingers down = 6
And there's the answer: 56
Narrator: It works for bigger or smaller numbers. Just imagine negative fingers and extra fingers.
Flame-haired character (excited): I'm so powerful.
Flame-haired character: Is this you right now? Why?!
Narrator: See if you can figure it out before moving on.
Here's the proof:
10[(x-5)+(y-5)] + 1[(10-x)*(10-y)]
(labeled: 10 times sum of up values) + (labeled: 1 times product of down values)
= 10x + 10y - 10x - 10y + x*y
= x*y
Narrator: Now that you've seen the proof, you know fully why it works.
Flame-haired character: But... why?
Flame-haired character: Right, but how?
Flame-haired character (distressed, staring at "x*y"): It still seems like magic.
Narrator: This is the worst thing about being human.
*Source: The Puzzler's Elusion, by Dr. Dennis Shasha, who apparently got it from "a smart and elegant Polish woman."
Votey:
Caption: Me, all day Friday:
Bearded man (hand on chin, amazed): This is the coolest thing ever! Someone needs to inform the President!
Alt text
A tall black-and-white SMBC comic explaining a finger trick for multiplication. Title: "It's called 'Polish hand magic.'" A drawing of a fist labeled "One palm is worth 5." To multiply 7x8, you raise fingers: on one hand raise 2, on the other raise 3 (the amounts above 5), and lower the rest. The fingers raised (2+3=5) give the tens digit, and the fingers folded down multiplied (3x2=6) give the ones digit, yielding the answer 56. A narrator notes it works for any numbers if you imagine negative and extra fingers. A flame-haired stick figure exclaims "I'm so powerful," then becomes confused ("Is this you right now? Why?!"). The comic then shows the algebraic proof: 10[(x-5)+(y-5)] + 1[(10-x)*(10-y)], labeled as ten times the sum of the up values plus one times the product of the down values, which expands to 10x + 10y - 10x - 10y + x*y = x*y. The narrator says "Now that you've seen the proof, you know fully why it works," but the character keeps despairing ("But... why?", "Right, but how?") while staring at the equation, saying it still seems like magic. Final caption: "This is the worst thing about being human." A footnote credits The Puzzler's Elusion by Dr. Dennis Shasha. Votey: a panel captioned "Me, all day Friday" shows a delighted bearded man with his hand on his chin saying "This is the coolest thing ever! Someone needs to inform the President!"
Transcribed by Claude Opus 4.8.