Clicking on the buttons "C1", "C2" and "C3" we can change the colors of the
squares that represent hundreds, tens and units in the added numbers. The added numbers need colors only for tens and units. All selected
colors are shown near the upper right corner of the applet. To achieve the best
visualization it is a good idea to select different colors for hundreds, tens and units.
To add 16 and 25 select 1 from the left digit column, click on it and click on the
first "10" button in the second row of the applet. Then the first square in the column
under the "10" button will be colored showing that 16 contains a one full ten. Do the
same with 6 but this time click on the first "1" button in the second row of the
applet. Now the first six squares right below the "1" button will be colored. These
two operations will also produce the number 16 in the last row of the applet.
Do the same with the number 25 using the second "10" and "1" buttons in the
second row of the applet. Proper numbers of squares will be colored representing
the number 25 and now in the last applet row there will be visible the expression 16
At this stage you can modify any of the inserted numbers. As a matter of fact an
order of digit insertion and modification is irrelevant. You can do it until you click on
one of the two equality buttons. This click triggers the appearance of the addition
result and the colored squares visualizing it. Simultaneously the applet is ready for
the next addition operation.
Besides addition this applet can perform the subtraction of two digit
nonnegative numbers. To enter the subtraction mode click on the "+" button in the
upper left corner of the applet. All three "+" buttons will turn into "-" buttons and the
applet will be able to perform the subtraction. If the result is negative, the negative
sign will appear in the front of it and the colored squares (not white) will appear as
Clicking on the "-" button in the upper left corner of the applet restores the