Consider, instead of asking folks to type random digits, to multiply all the digits of their phone number and all the digits of their age together. If their phone number or age includes a zero, they can skip it, or they can combine it with the immediately preceding number. So if they’re 52 and their number is 336-555-1031, they can do 5x2x3x3x6x5x5x5x1x3x1, or they can do 5x2x3x3x6x5x5x5x10x3x1 .
This will be easier to understand, and should result in a pretty good spread of digits.
That’s a great option for a first try. But still we don’t want too many 5’s in their phone number. Someone do it with your phone number.
Including my age, it’s 61931x20
I told you not to use a 5. 
I’ve got a trick for you while we’re waiting standby.
What? You didn’t say that.
tell you what, figure out what you want the trick to be, and lemme know. This is getting a little frustrating.
I’m teasing. The answer is 5. I’ve got more please wait.
D’oh! I apologize, misunderstood you. My bad. Yes, the missing digit is 5!
I’ve got more but it’s a busy day at work moving furniture.
If you’ve followed me here you know I like math and computers especially hex numbers like 0x80 to calculate the tropical year length. I will use 0x100-1 to calculate your Bday which you didn’t tell me.
=LN(2)+5.5
Sorry only 6 digits of precision available with this old fashioned calculator I’m using. Almost your Bday.
I mean phone number. I mean phone number and age. You know what I meant when you type it in…
On the other thread we’ve been talking about 3,4,5 and e. Here we talked about 5. I can do all 8 digits of your hash.
=3 *4 *5 +2.71827 -SIN(SQRT(5))
If I might gently offer some well-meaning feedback. Such a complicated set-up leaves many people unsure as to whether what you are doing is incredible or not.
I could barely follow what you were asking and it seemed too convoluted to spark my interest. There may be the seed of an interesting trick there but it lacks a bit of sparkle at first pass.
My impression, too. People may prefer to solve my crossword puzzle instead.
It’s not that complicated. The rules are few. I only suggested some guidelines on how to choose numbers randomly.
Simply:
Multiply single digit numbers on your calculator
Let’s try it?
Or do it Left Hands way (above)
For a little background, I teach an afterschool magic club to kids, and also teach math magic tricks as part of my math lessons for grades 3-5. A good trick is going to be foolproof, is going to have unambiguous directions, is going to walk the audience through their steps in a way that doesn’t feel onerous. If the audience can deliberately or inadvertently mess up the trick, that’s not their fault, it’s the magician’s.
Try writing out your directions as numbered steps. Eliminate any places where there’s ambiguity, or where a person could accidentally mess up the trick.
It would help to provide an example of what we are supposed to do STEP BY STEP.
So that everyone can understand.
And then we can mimic.
How about that?
Let’s keep it simple. Multiply single digits on your calculator. For example:
5x3x7x9x2x6x8x6x2x4…
Type your answer here replacing the hundreds place with an X
Try to avoid using 5 or 1 too many times. Otherwise you will end up with a bunch of 0’s at the end.
I appreciate your help Left Hand
When I get some time to do this, I will probably participate.
So, I’m supposed to pick a one digit number, and multiply it 9 times by a one digit number at a time (without using 5 or 1 if possible). Then I’ll have to type the answer here replacing the hundreds place with an X. And you’ll guess the hundreds digit.
I’ll probably try it, but it doesn’t look much of a game. It’s a kind of funny/smart trick. Can it be developed into a game?
“too many” is ambiguous, and not an acceptable direction. You need to make this step unambiguous. Also, “1” won’t have this effect, but “0” will. Consider changing the direction: “Don’t use 0 or 5.”