| 摘要 |
A device for performing a calculation derived from a predetermined value, the device including: at least one sleeve with printed indicia, andat least two moveable assemblies, each with at least two sets of numerical data,wherein the sleeve has at least two means of displaying the numerical data,characterised in thatthe device is configured so it can be operated by the steps of v) aligning the predetermined value in the first set of numerical data on the first moveable assembly with a first display location on the sleeve so that an intermediate number in a second set of numerical data on the first moveable assembly is displayed at the second display location, and vi) aligning an approximate intermediate value from the first set of numerical data on the second moveable assembly with a third display location on the sleeve, so that the appropriate numerical result in the second set of numerical data on the second moveable assembly is displayed in the fourth display location of the sleeve.
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