The Jinx & Birthday Puzzles 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: 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? 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?