# Digi-Block.

Digi-Block, gr. 2-4. Starter kit contains 300 blocks, 30 tens holders, 3 hundreds holders, 1 thousands holder, three-place digi-counter, desktop place mat, 0-9 digi-flip card books, 1 array mat, 1 teacher's guide, \$119.98. Delta Education, 125 Walnut St., Watertown, MA 02472, (617) 926-9300.

The Digi-Block product is a manipulative set designed to teach students about the base-ten nature of our number system. The attribute that distinguishes it from other base-ten manipulatives is the way that the blocks fit in a container that looks like a larger version of the smaller block yet is easily unpacked into its unit equivalents. For example, ten unit blocks pack inside a ten-block, which then looks exactly like a unit block, but larger.

The set comes in three levels--grades K-l, 1-2, and 2-4. Each level includes unit digi-blocks; holders for tens, hundreds, and thousands; place-value mats; number cards; number lines; and a packing template counter. The counter shows when it is time to pack together blocks to make a larger bundle. Also included are activity books and teacher-reference guides. The level 3 set also includes array mats for multiplication and division work.

The print materials and the instructions in the teacher's guide are clearly written. In addition to presenting lessons, how-to-use activity sheets, and games to play, the teacher's guide also describes the theory of use and includes many management hints. The company also provides in-service training and consultant help.

Individual blocks are a little smaller than a domino, and the full set of several thousand blocks is rather bulky both in space and weight. Starter sets are available that are appropriate only for individual or small-group use. Teachers will have to decide whether having a model of the number system that bundles and unbundles easily and looks the same as it grows is worth the money and space that this set requires. Considering the price of starter sets, which run from \$50 to \$120, might be a way to make that determination.

COPYRIGHT 2000 National Council of Teachers of Mathematics, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.