Direct Variation

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Direct Variation

• The graph of a direct variation is always a
  line that passes through the origin.

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Direct Variation

• When two variables are related in such a way that
  the ratio of their values always remains the
  same, the two variables are said to be in direct
  variation.

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Definition

• A direct variation can be described by an
  equation in this form
• The letter k represents the constant of
  variation.
• You say that y varies directly with x.

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• If y varies directly as x and y 8 when x 12,
  find k and write an equation that expresses this
  variation.

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• If y varies directly as x and y 24 when x 16,
  find y when x 12.

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To Do.in groups of 3/4

• In both inches and centimeters, find the length
  of
• One shoe in your group.
• The smallest assignment book in your group.
• The youngest persons index finger.
• The oldest persons wrist.
• The other persons wrist to elbow.
• Make a scatter plot of these data. Decide as a
  class which unit to put on the x-axis.
• Find a line of fit.
• Identify and interpret the meaning of the slope.
• Identify and interpret the meaning of the
  y-intercept.
• Is this a direct variation?

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