Abstract: A base member has a plurality of upwardly facing openings for receiving arithmetic value blocks such as addition or subtraction blocks, a first upwardly facing end opening for receiving positive answer blocks and a second upwardly facing opposite end opening for receiving negative answer blocks. A summing rack including transverse gear teeth is slidably mounted in a longitudinal slot in the base member communicating with each of the recesses. One end of the summing rack has an encoded pattern of holes defining the numerical values of possible positive answers; and the other end of the summing rack has a similar series of holes defining the numerical values of possible negative answers. Each of the recesses which receives an arithmetic value block has a sector gear therein which engages the summing rack teeth and moves the rack a proportionate distance when an addition or subtraction block is inserted into the corresponding recess.

Abstract: A system of children's blocks for teaching arithmetic, comprising various types of arithmetic operation blocks, and a number of answer blocks. Each block is dimensioned in accordance with a predetermined numerical value. Addition blocks contain a linearly slidable rod having a portion protruding from the block a distance corresponding to a numerical value printed on the block. When two or more addition blocks are aligned, the rods of said blocks push against each other, to cause the rod of one of the end blocks to protrude a distance corresponding to the sum of the values of the mutually engaged blocks. An answer block contains an internal flag member and a visible indicator positioned so that an indication of correct result is displayed only when the protruding portion of the rod of an engaged addition block corresponds to a value associated with the answer block utilized.

Abstract: A system of children's blocks for teaching arithmetic, comprising various types of arithmetic operation blocks, and a number of answer blocks. Each block has a rod dimensioned in accordance with a predetermined numerical value. Addition blocks contain a linearly slidable rod having a portion protruding from the block a distance corresponding to a numerical value printed on the block. When two or more addition blocks are aligned, the rods of said blocks push against each other, to cause the rod of one of the end blocks to protrude a distance corresponding to the sum of the values of the mutually engaged blocks. An answer block contains a "Yes" light and/or an audible bell chime coupled to electrical sensing switches which are positioned so that an indication of correct result is displayed only when the protruding portion of the rod of an engaged addition block corresponds to a value associated with the answer block utilized.