sub3

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Most 2nd and 3rd graders struggle with subtraction problems that require borrowing. Having to strike-through numbers and then stack new numbers above them is a confusing process that leads to frustration and under achievement. Here is the answer: let the student step through a prompted sequence and be checked as he/she goes. Let the student concentrate on the essential arithmetic without having to worry about doing neat strike-through's and lining up columns of new numbers. Your child/student will appreciate the neat tableau that is generated as he/she follows the prompts and answers the questions. The prompts consist of either a yes/no question regarding whether a particular column needs to borrow or question marks where the new numbers should be in the normal borrowing tableau (“?” if a single digit answer is expected, and “??” if a 2 digit answer is expected). The question marks are automatically replaced by numbers entered from the virtual numeric keypad occupying the lower part of the screen. If the student accidentally presses the wrong numeric key, it can be erased by the “del” key and re-entered. All numeric entries are committed by tapping the “done” virtual key. If the student commits an incorrect answer, the error count is incremented, and he/she is instructed to try again. The student cannot proceed to the next step until the correct answer (numeric value or yes/no).

When the problem is complete both the student and the teacher/parent can see if any errors were made (and corrected) along the way before arriving at the final answer. Doing a sequence of exercises without errors will demonstrate that the skill has been mastered.

Most arithmetic programs follow the “electronic flashcard” paradigm: just present the problems for the student to work and score the response when the student is finished. This leaves the student to struggle through the solution with pencil and paper. If the student finally enters an incorrect answer, and the computer tells him so, the student has no idea what went wrong. In contrast sub3 provides prompts that present the student with a sequence of challenges and immediate feedback after each step. A tedious exercise is turned into a fascinating game. Another advantage of sub3 is that the numbers for each problem are generated randomly so the student will never see the same problem twice.

The extensive instructions included with this app provide comprehensive descriptions of all the steps involved in subtraction with borrowing, which will be a great help for the parent who needs to supplement what the student has learned in the classroom. This initial, free, version of the program uses only 3 digit numbers (hence the name sub3), which should provide sufficient problem variety to ensure the development of excellent student skills. If several thousand people install the free app, I will provide an extended version to allow the user to choose a larger number of digits, and charge a few dollars.