4.1
The Jinx |
Student's
page |

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:

- Did you get 13 in cell D10? Well, that means your number (6 in this case) jinxed you. You got 13 - the unlucky number!

- Make 3 additional columns.

- Highlight D3 through G10. (It forms a rectangle.)

- Choose Fill Right from the Calculate menu.

- Next enter different numbers in D3, E3, F3, G3 so it looks something like this. Try your own numbers.

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.

- Ask the participants to write down the number of the month of the year in which they were born.
- Write the number of the day they were born.
- Have them do the calculations listed below.
- Ask a participant what number they got. From that number the Math Magician hears, he or she can determine the personís birthday. See if you can figure out what he does.

- Month of Birthday
- The number of the day of birthday
- Multiply month by 5
- Add 7
- Multiply by 4
- Add 13
- Multiply by 5
- Add the day of the month

**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?)