| 摘要 |
The device uses a sliding card with pre-cut apertures to provide range of mathematically determined possible number combinations. The device for producing combinations of two or three numbers includes a sleeve (1) which is open at the top and bottom. The rear surface of the sleeve is longer than the front surface, providing a projecting area at the top of the sleeve. On this there is a set of rectangular windows in which numbers may be written. A card is provided to slide within the sleeve, so that it moves over the written numbers. The card has a series of rows of apertures (4) cut into its surface, so that as the card slides vertically (5) within the case different combinations of two or three numbers can be displayed from the written row. The pattern of cut apertures is devised mathematically to ensure all possible combinations are provided.
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