Number Walls from the Top Down: Subtract to Find the Bricks

The top brick is filled in on every wall here, which is the opposite of how a number wall usually arrives. Six three-course walls are printed across this 1st grade number-walls page, and each one already carries three numbers: the single stone at the top, one brick in the middle row, and one along the base. The first wall reads 17 at the top, a 9 beside an empty brick in the middle, and a 7 in the corner of the base. Three bricks in each wall are outlined in dashed orange and waiting, and the rule at the head of the page is unchanged: every brick is the sum of the two beneath it.

Turning the wall upside down turns addition into subtraction without ever printing a minus sign. If the top is 17 and one brick under it is 9, the other has to be 8, and the child arrives at that by asking what goes with 9 to make 17 rather than by taking anything away. That is the missing-addend question, the most useful form subtraction takes at this age, and here it appears three times in every wall with a structure holding it together. The tell is which children run out of anywhere to start: the wall can only be entered where two of the three numbers in a triangle are known, and finding that entry point is half the task.

Print the PDF free and let the first wall be talked through aloud, naming each step as a question, 9 and what makes 17, before anything is written. Number walls to 20 is the ordinary direction, built upward from a printed base, and the missing brick page sits between the two with a hole in the bottom row. Once the walls make sense in both directions, number walls with two-digit answers takes the same structure past twenty.