In Which I Emulate Penn and Teller

Yesterday John and I went to New Orleans to see Jersey Boys with the “Golden Oldies” group associated with a local hospital. (The group is actually called “Golden Opportunities", but I like my name better.) While we were riding down on the tour bus, the organizers gave us a few handouts to help us while away the time. One of them read (I copied the punctuation from the original):

It does work, unless you have already had your birthday this year. It has to work, because this is what you are doing:

1. Take your shoe size.

We’re going to call your shoe size “x”.

2. Multiply it by 5.

That gives you 5 x.

3. Add 50.

That gives you 5x+50.

4. Multiply by 20.

And now you have 100x + 1000

5. Add 1012.

That gives you 100x + 2012. Does that “2012” look familiar? It should, because up until 25 days ago (as of this writing), it was the current year.

6. Subtract the year you were born.

100x+ 2012 minus your birthdate gives you 100x + your age! Well, it gives you your age unless your birthday for 2013 has already passed. Apparently there weren’t many Capricorns in our group. Apparently there weren’t any centenarians, either, because if you are 100 years old or older, this trick won’t work.

So now you have a three or four digit number. The last two numbers are your age, because, as we see above, what you have done is subtract the year you were born from what was the current year when this trick was last updated. To your age, you have added your shoe size multiplied by 100, so yes, of course, you get the digit that represents your shoe size in the 100’s place, because math.

You, too, can dazzle your friends! Just take some simple arithmetical calculation and break it into parts. Instead of telling them to multiply a number by 100, tell them to multiply it by 5, and then a few steps later, to multiply it by 20. Interlace another simple arithmetical calculation, breaking up the steps for it. Instead of telling them to add 2013, for instance, tell them to add 50, multiply it by 20, and add 1013. You can take the trick above, substitute the number of cups of coffee they had today for their shoe size and the date they got their driver’s license for their birthdate. Then you can tell them that the number of cups of coffee they had today can tell them how many years they have been driving.

It’s magic!