Base blocks consist of individual "units," "longs," "flats," and "blocks" (ten of each set for base 10). They can be used to show place value for numbers and to increase understanding of addition and subtraction.

When this virtual manipulative first loads, you are asked to complete an addition problem using base blocks. Click the button to obtain a new exercise. The addition of the blocks is accomplished by using the grouping procedure described below.

Exchanging and grouping pieces

You may drag a base block into a column to the left or back to its appropriate column, but when you move a block one column to the right, it breaks apart to show that you have made an Exchange (as, for example, a 10-long is exchanged for ten units, or a 5-flat is exchanged for five 5-longs). To group pieces to make an exchange the other direction, click and hold the mouse key down while dragging a rectangle to "lasso" the pieces. Thus, in base 5, you can "lasso" five units to make a long piece or you can lasso five flats to make a block. The newly grouped object can then be dragged into the next column.

Set the base

To change the default setting (base 10), first click . Then you can click the up or down arrow buttons to change the base. You can work with base blocks for any of the bases 2, 3, 4, 5, or 10. All problems and numbers will be represented in the base shown.