1 Answer

   The difference between a ruler and a straight edge is that while either can be used to mark a straight line, only a ruler is divided up into segments allowing one to take measurements of something.

If one needed to draw a straight line across a piece of paper, for instance, either a straight edge, or a ruler would suffice. If, however, one needed to draw an exact 2 inch line, a ruler would be required to find the exact distance to 2 inches.

Rulers will typically be marked in either the metric, or the imperial system, the imperial system (base 12) being what most American are used to seeing: inches, feet, and yards (in the metric system 1 inch is 2.54 centimeters, 1 foot is 0.3048 meters, 1 yard is 0.9144 meters).

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