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Eraser inventory


This game appears in Grade 4, Chapter 3, Lesson 5.

Students have been studying an Eraser Store that, up until now, packaged all of their erasers in sevens. There were seven erasers in a "pack," seven packs in a "box," and seven boxes in a "crate." Now, the Eraser Store has ordered some larger packages! Erasers will now be packaged in tens. There will be ten erasers in a "pack," ten packs in a "box," and ten boxes in a "crate."

This game asks students to work with this new packaging system, which is actually the familiar base-10 system they've worked with from their first experiences with numbers up until they met the Eraser Store. They'll use the new insights they've developed about re-grouping in their work with packages of sevens and their previously-acquired skill with packages of tens to keep track of the inventory of erasers under the new system.

Brief rules

How to Play the Game:

  • This is a game for two players. Each player will need a number cube and a copy of AM15: Eraser Inventory. (Players can also record their inventory on their own sheet of paper. This should have columns for crates, boxes, packs, and loose erasers.) The game begins with a stock of 5 crates of erasers, and the store accepts only orders that are smaller than a crate.
  • Player 1 tosses the number cube three times.
    • The first toss gives the number of boxes in the order.
    • The second toss gives the number of packs in the order.
    • The third toss gives the number of loose erasers in the order.
  • Player 1 records the shipment in the spaces for the first shipment.
  • Player 2 then figures out how many crates, boxes, packs, and loose erasers remain in stock. Player 2 records the numbers in the spaces for "New amount in stock."
  • Players switch roles. (Player 2 now tosses the number cube to create an order, and Player 1 finds the new amount in stock after the order has been filled.)
  • The game is over when one player rolls an order that is too large for the store to fill. The last player to have a completed order is the winner.


Original Packaging Version:

  • Eraser Inventory can also be played earlier in the chapter with the original packaging system. In this variation, there are seven erasers in a pack, seven packs in a box, and seven boxes in a crate. Keep in mind that after you've switched from packaging by sevens to packaging by tens there isn't really a reason for your students to go back to the old system.

Action Warehouse Version:

  • Another possible variation is to have each player flip a coin at the beginning of a turn to determine whether the roll will be a shipment (erasers subtracted from the inventory) or a delivery (erasers added to the inventory). Heads could be a shipment and tails a delivery. This game will need different conditions for determining when the game is over.
    • Play the game cooperatively as time allows or until the inventory sheet is full.
    • Play competitively to match a guess about the final outcome. Each player writes either "more than five crates" or "less than five crates" on a piece of paper and keeps it hidden. Then, when they've finished filling out the inventory sheet or time is called, they see how many erasers are left in stock. If a player's guess is correct, the player wins. In this variation, it's possible for both players to win or for neither player to win!
4th Grade Chapter: