

inidyls Veteran user NYC 315 Posts 
A friend and I were talking last night about math and magic. It's amazing what happens when you mix the two together. So we were thinking way back to some oldies and here's and old one you might remember.
1. use the first 3 digits of your phone # 2. multiply by 80 3. add 1 4. multiply by 250 5. now add the last 4 digits of your # 6. repeat step 5 again 7. subtract 250 8. now divide by 2 That's just one of the many math tricks we remembered. There's a lot of good ones. 
Necromancer Inner circle Chicago 3071 Posts 
There are certainly a lot of them  but a lot of good ones?
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gibby357 Veteran user The Woodlands, TX 344 Posts 
You guys must like math. I was with you upto the point where I had to multiply. When you ask for someone to think of their own phone number, that is good, you have made it personal. When you ask them to multiply that by 80 you are making them work. When you then request that they multiply by 250 some will be going to the bathroom or striking up a conversation with the cute blonde sitting next to them. I won't even go any further. I am sure the picture is becoming quite clear.............
gibby 
kihei kid Inner circle Dog House 1039 Posts 
For what it's worth, I liked it Inidyls.
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You brought something beautiful to this world, you touched my heart, my soul and my life. You will be greatly missed. Until we meet again “my old friend”. 
J.Warrens Inner circle Canada 1098 Posts 
Greetings!
That is a very nifty thing! Not something I'd use but definitely a fun bit to play with. Thanks for sharing> Cheers, J.Warrens 
landmark Inner circle within a triangle 5156 Posts 
Check out the Magical Equations forum for some excellent thinking from some very clever minds concerning math based effects and presentations that win over even people who dislike math.
But then again, maybe we'll just keep it our little secret . . . Jack Shalom
Click here to get Gerald Deutsch's Perverse Magic: The First Sixteen Years
All proceeds to Open Heart Magic charity. 
Lee Darrow V.I.P. Chicago, IL USA 3588 Posts 
Inasmuch as I have what amounts to a dyslexia about math, anything that makes me have to dig out a calculator is NOT going to play in my head very well.
Heck, I even force a CARD to get the letter when doing the Grey Elephant in Denmark routine! As Michael Ammar said  use the KISS principle  Keep It Slogan Simple. But it does show nome very nice thinking. Keep that up, by all means! Lee Darrow, C.Ht. http://www.leedarrow.com
http://www.leedarrow.com
<BR>"Because NICE Matters!" 
MichelAsselin Veteran user 20th century, 3rd dimension 326 Posts 
Quote:
...anything that makes me have to dig out a calculator is NOT going to play in my head very well. Lee, keep your mind open to the fact that a great many people do lug an electronic agenda of some form with them these days... THEY will provide the calculator.
" , ? ; !!! "
 Marcel Marceau, Feb 30, 1945. 
Chout New user 52 Posts 
Quote:
On 20031112 08:32, gibby357 wrote: Funny but sadly true. Unless I already have a calculator nearby, I'd probably ignore someone who pulled this trick on me. 
Nir Dahan Inner circle Munich, Germany 1390 Posts 
In many math routines the real trick is to turn it into an interesting piece of performance. unfortunatelly sometimes it is just not possible  as in the effect above...

wayman Special user England  Sunderland 588 Posts 
I just don't get it....call me DOH!!!
Quote:
1. use the first 3 digits of your phone # What is this supposed to achieve??? does this only work with american phone numbers?? 
Scott Cram Inner circle 2678 Posts 
Quote:
On 20031228 09:10, wayman wrote: With any 7digit phone number, the answer will be the phone number itself. I imagine that the division by 2 is supposed to be done by the "mathemagician" without the spectator knowing about it. If you call the first three digits of your phone number "X", and the last four digits of your phone number "Y", then here's what happens: 1. x 2. 80x 3. 80x+1 4. 20,000x+250 5. 20,000x+250+y 6. 20,000x+250+2y 7. 20,000x+2y 8. 10,000x+y "10,000x" merely takes the 3digit number that is x, and places it in front of the fourdigit number that is y, resulting in the phone number. Quote:
On 20031228 07:43, Nir Dahan wrote: I don't know. How about introducing it as, "Did I ever tell you how I used to pick up girls at M.I.T.? First, I'd use my best opening lines, such as 'Let's convert our potential energy to kinetic energy' or 'Since distance equals velocity times time, let's let velocity or time approach infinity, because I want to go all the way with you'. Then, I'd get their phone number in this way . . ." "Oh, you're wondering how things went with that M.I.T. girl? We integrated from the very point of origin. Her curves were continuous, and even though I was odd, I was a real number. The day our lines first intersected, we became an ordered pair. From then on it was a continuous function. We were both in our prime, so in next to no time we were horizontal and parallel. She was awed by the magnitude of my perpendicular line, and I was amazed by her conical projections. "Bisect my angle!" she postulated each time she reached her local maximum. I taught her the chain rule as she implicitly defined the amplitude of my simple harmonic motion. We underwent multiple rotations of our axes, until at last we reached the vertex, the critical point, our finite limit. After that we slept like logs. Later, she found me taking a righthanded limit, that was a problem, because it was an improper form. I meanwhile had realized that she was irrational, not to mention square. She approached her ex, so we diverged." 
landmark Inner circle within a triangle 5156 Posts 
Hilarious Scott, thanks.
Jack Shalom
Click here to get Gerald Deutsch's Perverse Magic: The First Sixteen Years
All proceeds to Open Heart Magic charity. 
Chout New user 52 Posts 
You guys crack me up.
Btw, I never knew this: 1. x 2. 80x 3. 80x+1 4. 20,000x+250 5. 20,000x+250+y 6. 20,000x+250+2y 7. 20,000x+2y 8. 10,000x+y Thanx for explaining Scott. 
Dennis Loomis 1943  2013 2113 Posts 
In case you havn't thought about it recently, calculators abound these days because a great many cell phones have calculators built in. Makes some of this math stuff a little easier to do in today's world.
Dennis Loomis http://www.loomismagic.com
Itinerant Montebank
<BR>http://www.loomismagic.com 
wayman Special user England  Sunderland 588 Posts 
Thanks Scott.
So 1. use the first 3 digits of your phone # = 123 2. multiply by 80 = 9840 3. add 1 = 9841 4. multiply by 250 = 2460250 5. now add the last 4 digits of your # +4567 = 2464817 6. repeat step 5 again = 2469384 7. subtract 250 = 2469134 8. now divide by 2 = 1234567 Ahhhhhh now I get it. this only works if you do each equation separatley and not as one continuous sum. ie not (123*80+1*250+4567+4567250/2) wich would equal 19099 This was what I was doing wrong. 
drkptrs1975 Elite user North Eastern PA 452 Posts 
Here is a new twist, just have your friend do steps 16 and tell you their answer, you can do steps 78 in your head and tell them their phone number.

MRReed New user Lake Odessa, MI 58 Posts 
Wayman 
Your calculation list... (123*80+1*250+4567+4567250/2) ...will work, but... if you remember the "operator precedence" from your grade school days, you must perform muliplications and divisions before additions and subtractions, so you simply need to add parentheses to your 'formula,' and it will work: ((((123*80)+1)*250)+4567+4567250)/2) This gets the precedence correct. An interesting anecdote re "operator precedence" follows. One can prove that 1 = 0 algebraically by ignoring operator precedence, e.g.: Set value of x to 1: x = 1 Set value of y to 1: y = 1 Equate: x = y Multiple by x: x2 = xy Subtract y2: x2  y2 = xy  y2 Factor: (x + y)(x  y) = y(x  y) Divide by (xy): (x + y) = y Subtract 1: x + y  1 = y  1 Substitute: 1 = 0
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dlhoyt Regular user 176 Posts 
Quote:
On 20040319 08:42, MRReed wrote: This is not really due to operator precedence, but to division by zero in step 7. xy = 0 and division by zero is undefined. It is undefined to avoid the kind of problem that this example represents; if allowed, you can prove that 1 = 0, a contradiction. Serious consequences would ensue, so don't attempt this at home. 
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