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"Arithmetic Tutor - Addition" is an Android app that helps grade school students to learn and master the addition of whole numbers. The student selects the options for the exercise, such as the number of digits for each operands, whether to enable carry, and number of problems in each exercise. The app then generates the operands for each problems in the exercise based on the options selected. The student is given the opportunity to solve it, and the app will check the answer. If the answer is incorrect, the student can either try again, or ask the app to show where the mistake(s) is/are, or ask the app to show the steps to solve the problem. All instructions are verbal, with the option of displaying the verbal instructions as text. The score for the exercises are recorded, and can be retrieved to find out the student's progress.

Please take a look at this video to get an idea on how this app works.

The following are the screen shots and descriptions of the most important functionalities of the app.

The Main UI page lets the student to select the addends (i.e. the operands) size, whether to enable carry, the number of problems in the exercise, and whether to display the verbal instructions as text. When the student is satisfied with all the options, he/she can start the exercise by touching the Start Exercise button.

The exercise starts with generating a problem with operands that is generated randomly, but at the same time satisfies the criteria selected in the options from the main UI page. If carry is enabled, the operands are generated in such a way that not all place position addition will result in a carry into the next place all the time. This is to prevent the student from mistakenly believe that carry is always needed. The student can solve the problem by dragging and dropping digits from the bottom row of digits, onto the carry and answer digit positions indicated by a faint grid of boxes displayed during the drag and drop process. If a digit was landed on an incorrect position by mistake, it can be removed by dragging it away from any grid position. Once the student is satisfied with the answer, a long press on a display area that does not have a digit that can be dragged will invoke the context menu.

The context menu lets the student choose from a set of options:

• Check Answer - lets the app checks if the student's answer is correct. This option will only be shown after the student has at least entered one digit into the problem.
• Show Me - ask the app to show the steps to solve the problem.
• Next Problem - moves on  to the next problem.
• Show My Score - displays a list of exercises that the student has completed, and lets the student choose one of the exercises to display the scores. The exercises are listed in chronological order, with the most recent one on top.
• Cancel - if the context menu is invoked by mistake (for example, while attempting to drag a digit), it can be dismissed by hitting Cancel to return to the problem.

Note that the items in the context menu can change, depending on what the student is doing at the time. For example, if the app is doing Show Me, the context menu will contain an item to Stop Show Me.

 

When Check Answer is selected from the context menu, the app checks the student's answer and if it is correct, it will move on to the next problem. If the answer is not correct, then it pops up this dialog to let the student choose to either "Try Again", to go back and try fixing the mistake(s); or "What's Wrong", where the app will show where the student had made the mistake(s); or "Show Me", where the app will show the student how to solve the problem step by step. The instructions in both "What's Wrong" and "Show Me" are given verbally, with an option (from the Main UI menu) to display the text of the instructions.

When "What's Wrong" is finished, the display will be shown as in the left, where any incorrect answer or carry digit(s) will be highlighted in red with a red cross on the digit position.

Note that once the app has shown the student where the mistake(s) is/are, in the answer, the student will no long be allowed to change the answer by dragging or dropping digits. The student can, however, still invoke the context menu. For example, to select Check Answer again to see where the mistake(s) is/are made, or choose another context menu option.

Also, while the app is showing where the mistake(s) is/are, the student can invoke the context menu and select the "Stop What's Wrong" item to terminate What's Wrong.

When Show Me is selected from the context menu (or from the pop up dialog box from Check Answer, when the answer is wrong), the app will show the step by step instructions on how to solve the problem. The steps will be shown as though the student is entering the answer by dragging and dropping the digits. And each step will be accompanied by a verbal instruction on what needs to be done.

Note that once the app has shown the student how to solve the problem, the student will no long be allowed to change the answer by dragging or dropping digits, and Check Answer will no longer be available in the context menu. The student can, however, still invoke the context menu. For example, to select Show Me again to see the instructions on how to solve the problem, or choose another context menu option.

Also, while the app is in Show Me, the student can invoke the context menu and select the "Stop Show Me" item to terminate Show Me.



When Show My Score is selected from the context menu, a list of completed exercises is shown to the student. Each exercise is associated with the date and time when the exercise is done. The list is displayed in chronological order, with the most recent exercise on top. The student (or parent, or teacher) can select one of the exercises to review the scores.

Note that this list only shows exercises that were completed. That is, the student has done all the problems in the exercise. If the student exited from the exercise session prematurely, by hitting the Back button on the device, no partial credit is granted, and the score for the exercise will not be saved.

When an exercise is selected from the list of exercises, the score for that exercise is shown, as in the left. The score shows the time and date when the exercise is done; the operation, in this case, Addition; the operands size for the exercise; whether carry is enabled for the exercise, and the total number of problems in the exercise. The app kept track of the number of correct answer(s) the student gotten on the first try, and the number of answer(s) the student gotten correct from more than one tries. And two scores are calculated based on these two values.