| 摘要 |
This disclosure relates to a calculator and comparison device for use by shoppers in determining the most economical brand or package of a variety of brands or sizes of the same product. The device has a center disc which has a series of logarithmic scales which are marked-off in indicia of dollars and cents values, and an outer disc which is carried on the center disc which has a logarithmic scale measured in standard weight measure units. The outer disc is smaller in diameter than the center disc thus permitting the scales on the center and outer discs to be read simultaneously. The center disc and the outer disc are rotatable with respect to each other about their center axis. A transparent member is rotatably secured on the outer disc and is associated with the center and outer discs. The transparent member has a scale marked-off in indicia of units, cans, boxes, etc. The scale on the transparent member may be superimposed over the scales on the center and outer discs, thereby permitting the three scales to be read and used simultaneously. Some means to reduce friction is provided between the center and outer discs so that the outer disc and transparent member can be rotated together about the center axis of the disc without moving the center disc.
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