This worksheet will generate advanced subtraction drills as selected by the user.
The user may select from 256 different subtraction problems from addition tables ranging from 0 to 15.
The user may also select a 1 minute drill of 20, a 3 minute drill of 60 problems, a 5 minute drill of 100 problems, or a custom drill with ranges from 20 to 100 problems and times of 1 to 5 minutes.
The problem array contains 256 elements (check boxes) that correspond to different subtraction problems.
Each element (check box) will produce a problem that matches the corresponding top and bottom numbers.
These check boxes will product problems with POSITIVE ANSWERS.
These check boxes will product problems with ZERO AS THE ANSWER.
These check boxes will product problems with NEGATIVE ANSWERS.
ALWAYS select enough problems from the array to fill the required number of problems of the Math Drill you wish to use, if you don't you WILL GET REPEATS.
The array will start out with everything selected, you may clear the entire board by clicking the Clear All link or you may select the entire board by clicking the Select All link located at the bottom of the array.
You may select/clear the rows and columns by clicking the icons for that particular row or column.