This is based on the activity Differs
Here's the Excel file I created: Difference Tuples
. I usually
right-click, "Save Target As", and select where I want the file to
You can see the given start numbers 100, 2, 37, 59 in the first
Here are the formulae I used (you can see these in the formula bar
when you click on each cell).
ABS calculates the positive difference.
Under 100, =ABS(A2-B2) this compares 100 with 2
Under 2, =ABS(B2-C2) this compares 2 with 37
Under 37, =ABS(C2-D2) this compares 37 with 59
Under 59, =ABS(D2-A2) this compares 59 with 100, right back at the
Once I had all four formulae in and working correctly I highlighted
these four cells (A3 to D3). I then caught hold of the extreme,
bottom, right-hand corner of the highlighted area (the normal white
cross changes to a small thin black one), and I dragged down as far
as I wanted those formulae to be replicated. Excel created new
formulae which do the same job as the formulae in the top line, but
automatically adjusted the cell references so that they would be
correct for the new position.
Isn't it nice when you get answers that quickly? It leaves time to
ask more interesting questions.
Which set of start numbers gives the longest run before becoming 0
0 0 0?
How is the 4-number problem like a pair of 2-number problems
running side by side? How is it different? How is the 8-number
problem like a pair of 4-number problems running side by side? How
is it different?
Have I missed anything? Oh yes, the increment buttons:
So that I could change the start numbers quickly, and without
typing, I put in some scroll bars to control the values in the
first row. Look back at October 02
to find out about increment
buttons. They're very easy and let you keep your eye on the
numbers instead of the keyboard.