Calculator Tricks

You'll find lots of cool Calculator tricks on this page that will amaze friends and family.  Another way to get students to see how fun and cool math really is! 

Grab your calculator if you haven't yet, and let's Get Ready....Set....Calculate.... 

"Got Your Number" Calculator Trick

Have someone type in any number between 1 and 900 into the calculator without letting you know what it is.  (Actually, this trick will work for numbers greater than 900, but on most calculators the resulting display will not be large enough).  Also tell them to choose a number with mixed digits and it should be a positive number. 

Next, you will have them perform the following calculations......on the calculator of course (:

1. Multiply their number by 3.
2. Then multiply the result by 7.
3. Then multiply the result by 37.
4. Then multiply the result by 11.
5. Finally multiply the result by 13.

Now ask them to show you the number showing in the calculator. 

Ok, now here's the magic! By looking at this number, you will be able to reveal the number they started with. For example, let's say the random three digit number they first entered into the calculator was 763.  After performing all f the multiplications that you tell, they would end up with 84777693 on the display.

So, are you wondering how you come up with their starting number of 763?  Good, I thought you might want to know.  I'm going to explain below and with a little practice you'll be performing this trick in no time like a true "Mathemagician!"

Here's How It Works.....

We start the trick by multiplying by 3, 7, 37, 11, and 13.  But guess what...

3 x 7 x 37 x 11 x 13 = 111,111

So really, we are just having the person multiply their original number by 111,111. 

Depending on what three digit number they choose at the start of the trick, their final number will appear in one of the following formats below. Don't worry, I'll explain.  I'm going to do a few examples.

H S S S S S V
H S S S S V F
H H S S S V V F

H = "Head" - It will consist of one, or two, or no digits.

S = "Stem" - It will consist of easily identifiable REPEATING digits, always located in the center.

V = "Variable" - It will consist of one, or two, or no digits.

F = "Final" - It will always consist of a single digit.

Just hang with me, it's not that bad...  I'm going to do a few examples so you can see exactly what's going on, okay...

After you memorize the format above, here's what to do next.

1. Subtract the "variable" V or VV from the SAME number of digits in the "stem".
2. Subtract the difference obtained in step 1 from the entire "head" H or HH.
3. Attach the final digit to the difference you obtained in step 2. This is the number your friend used!

Example 1:  Your friend chooses the number 257.

After you get your friend to goes through all of the multiplications on the calculator, their final result for this example will be 28555527.

Head: 28

Stem: 5555

Variable: 2

Final: 7

Step 1: 5 - 2 = 3

Step 2: 28 - 3 = 25

Step 3:  Attach 25 to 7 to get 257.

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Example 2: Your friend chooses the number 632.

After you get your friend to goes through all of the multiplications on the calculator, their final result for this example will be 70222152.

Head: 70

Stem: 222

Variable: 15

Final: 2

Step 1: 22 - 15 = 7

Step 2: 70 - 7 = 63

Step 3:  Attach 63 to 2 to get 632.

I'll be adding more calculator tricks as I get them so be sure to check back soon. Also, if you have any you think our visitors would get a kick out, please send them my way.

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