Four Number Constant (Subtraction Game) April 11, 2009

Posted by inspiremath in Addition/Subtraction, Math Games.
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● piece of paper for each team or whiteboard/chalkboard

Player or team selects any four numbers from 1-15 and writes them across his paper to form the beginning of four columns.  Proceed to take the first two numbers across, subtract the smaller number from the larger one, and put that answer under the first column.  Then take the numbers from columns 2 and 3 and subtract and put that answer under the second column.  When you get to the fourth number, use the number in the first column to subtract and get an answer.   Put that answer in the fourth colmn.  Continue this pattern in each row until all numbers are the same.  First player or team to do this, wins a point.  Teams could start with the same numbers and race each other, or use different numbers.  For example, if you wrote a 7,2,4 and 13 across the top, the next row would be as follows: 7-2 = 5, 4-2=2, 13-4=9, and 13-7=6.

7    2    4    13
5    2    9    6
3    7    3    1
4    4    2    2
0    2    0    2
2    2    2    2