Addition and subtraction activities with the Ten Land (base 10) blocks using a business model:
- Addition is modeled as importing the blocks to a warehouse in Ten Land. A truck arrives at the warehouse with a load of blocks and a packing slip designating the number and kind of blocks on the truck. Students unload the truck and put the blocks in the warehouse where ten the same must be traded for one of the next bigger block in keeping with the Law of the Land for Ten Land. For example, if a truck arrives with 7 unit cubes and there are already 8 of them in the warehouse, ten of the resulting 15 unit cubes would have to be traded for a long, resulting in 1 more long and 5 unit cubes in the warehouse. The addition problem thus modeled is the number and kind of blocks on the truck being added to the number and kind of blocks already in the warehouse.
- Subtraction, being the reverse of addition, is modeled as exporting the blocks from the warehouse. An empty truck arrives at the warehouse with an invoice listing the number and kind of blocks that are to be taken from the warehouse and put on the truck. If there aren't enough of a particular block to satisfy the invoice, the next larger block is traded for ten of the block in question so as to have enough. For example, if a truck arrives with an invoice for 5 longs and there are only 3 longs in the warehouse, a flat in the warehouse would be traded for ten more longs, yielding 13 longs in the warehouse, 5 of which would be loaded onto the truck, leaving 8 still in the warehoiuse. The subtraction problem thus modeled is the number and kind of blocks in the warehouse less the number and kind of blocks indicated on the invoice.
The activities are sequenced in order of difficulty from importing or exporting the blocks with (1) no recording to (2) recording just the answers to (3) recording the answers and the trades made to get the answers.
Grades K-6, 72 pages with permission to duplicate. Available as a downloadable e-book.