Abstract: An improved multi-segment, electronically-actuated display array that displays (a) a multiplication symbol configured approximately like “×”, and, centered in the same location, (b) one or more of an addition symbol, a subtraction symbol, and a division symbol configured approximately like “+”, “−”, and “÷”, respectively. A novel central segment or central segment group of the array displays a central portion of the multiplication symbol and of the other displayable arithmetic operation symbols—essentially the entire intersection of (a) the multiplication symbol and (b) a horizontal bar constituting the entire subtraction symbol, the horizontal portion of the addition symbol, and/or the vertically-centered portion of the division symbol.

Abstract: A learning aid for teaching arithmetic skills, that functions without an external source of electricity and weighs less than one kilogram, poses sets of problems to a user. The device has a question-probability-setting selector which allows the user to select—for practicing or testing—from among different groups of problems in which different problems have different probabilities of being posed. The device can pose sets of recently-missed questions by means of a missed-questions memory that stores a limited number of questions that a user—during one or more sets of questions—has most recently either answered incorrectly or failed to answer within a per-question time limit. The device generates an evaluative question-set score based on how well the user has answered a set of questions posed by it and stores and displays, one at a time, the scores for a limited number of the most recent question sets.

Abstract: An improved multi-segment, electronically-actuated display array that displays (a) a multiplication symbol configured approximately like “×”, and, centered in the same location, (b) one or more of an addition symbol, a subtraction symbol, and a division symbol configured approximately like “+”, “−”, and “÷”, respectively. A novel central segment or central segment group of the array displays a central portion of the multiplication symbol and of the other displayable arithmetic operation symbols—essentially the entire intersection of (a) the multiplication symbol and (b) a horizontal bar constituting the entire subtraction symbol, the horizontal portion of the addition symbol, and/or the vertically-centered portion of the division symbol.