# Economic Definition of total-marginal rule. Defined.

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**Term total-marginal rule Definition**: A mathematical connection between a marginal value is the slope of a curve of the corresponding total value stating that the marginal IS the slope of the total curve. If the total curve has a positive slope (that is, is upward sloping), then marginal is positive. If the total product has a negative slope (downward sloping), then marginal is negative. If the total curve has a zero slope (horizontal), then marginal is zero. Moreover, if the total curve has an increasing slope (becoming steeper), then the marginal is rising. If the total curve has a decreasing slope (becoming flatter), then the marginal is falling.

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