Abstract: Provided is an apparatus for teaching calculation skills. The apparatus may include a plurality of beads and a set of columns of the cells being configured to be occupied by one of the beads. The apparatus may include a set of sensors configured to determine occupation of the cells by the beads, and a processing unit electronically coupled to the set of sensors. The processing unit can be configured to: receive from a server at least one array of integer numbers. Each of the integer numbers represents an intermediate result of solving of a sequence of mathematical operations displayed to a user; determine, via the set of sensors, occupation of the cells by the beads; translate the occupation of cells to a check number; and compare the check number to a current number in array to determine whether the current operation is solved correctly.