A slide rule for solving time/speed/distance problems where distances are measured with a single or universal ruler applicable to all charts or maps regardless of scale. Result is achieved by printing alongside time entries on the slide rule a row of appropriately-spaced numbers constituting indicia of chart or map scale, and which has a range encompassing the largest and smallest scales of charts or maps which are likely to be encountered. When such numbers are properly positioned, it is necessary only to set chart scale opposite speed made good, after which running time will always appear opposite distance travelled, and vice versa. This device eliminates the need to use dividers and mileage or latitude scale, and thus obviates the intermediate steps which their use entails.