4.1 The Jinx
Student's page
Solution to the chocalate math problem
Here is a puzzle that will always jinx you.
Follow these steps.

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

Try it with three different numbers.
Do you think it will always work? Why do you think that?
To see if it always works, make a spreadsheet model of this puzzle.

Here's how:

  • Open Appleworks (or Excel)
  • Type in the text as you see it above.
  • Enter the formula =D3 + 11 in cell D4
  • Enter the formula =D4 * 6 in cell D5.
  • Continue until you have entered the formulas for cells D6 through D10.
  • After you finish entering the formulas, enter a numeric value in D3, like 6.
  • Look at cell D10. Does it show 13? (If not, check your formula in D10.)
  • Did D10 show 13? Try a different number in D3. What happens?

  • Can you find a number that will not always end up as 13?

    If not, why not?

    4.1 (B) Birthday Puzzle

    Create the birthday problem spreadsheet for the puzzle below. See if you can figure out what has to be done in order to figure out how this "mind reading" trick works.

    Here is the information the "magician" asks for Build the spreadsheet. Collect some data. From the data see if you can figure out whatís going on.. Add one more row to the spreadsheet called "the secret formula" so that the birthday is revealed.  

    Hint: If your birthday is on November 5th the number you should get from the spreadsheet is 1310. How can you find the date of your birthday from that number? (Hint Your birthday is 1105 so what if you subtracted 205 from 1310?)

    Back to problem page