The Famous Jinx Puzzle
Here are the steps for the Jinx puzzle.

Pick a number     ________
Add 11               ________
multiply by 6      ________
subtract 3         ________
divide by 3         ________
Add 5                ________
Divide by 2        ________
Subtract the
original number   ________

Answer:             ________

Does it always work? Try it with 3 different numbers.


Do you think you will always get 13 no matter what number you try?

The Jinx Calculator
To help you find out if this puzzle will work for all numbers, we will use a special spreadsheet “calculator”. Here is what it looks like:



Here is how to make it:
· Open a spreadsheet application (Excel)
· Type in the text as you see it above.
· After you finish entering the formulas, enter a number (like 6) in B1.
· Look at cell B8. Does it show 13?



Did you get 13 in cell C10? Well, that means your number (6 in this case) jinxed you. You got 13 - the unlucky number! Can you find a number that will make the puzzle not end in 13? Do you think it is possible? (Try numbers like: 2.5, -56, 3000, 999999999, .000005)

Can you try an irrational number like Pi? What's the problem?

Let's try a different way to answer the question. Start with the puzzle again...

Step 1: Pick a number.
Instead of picking a specific number, let’s choose to use something that could represent any number. Let’s use a bag.


The bag can contain any number you pick.

Step 2: Add 11



To show 11 we will use 11 small circles or “marbles”. Now we have a bag and 11 “marbles”

Step 3: Multiply by 6


We have 6 bags and 66 marbles.

Step 4: subtract 3


Now we have 6 bags and 63 marbles.

Step 5. Divide by 3


2 bags and 21 marbles.

Step 6. Add 5



2 bags and 26 marbles

Step 7. Divide by 2



1 bag and 13 marbles

Step 8: Subtract the number you picked in step 1.



But that’s the bag. You subtract the bag! So you are left with 13 marbles or just plain 13.