Direct Variation (1)

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Direct Variation
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Definition

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

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Example No. 1

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

• STEPS
• Write the equation.
• Substitute y by 8 and x by 12.
• Divide both sides by 12.
• Express your answer in lowest term.
• Substitute k to the equation.

?????? 812?? 8 12 12?? 12 ?? 2 3 ?? 2 3
??
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Example No. 2

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

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

• STEPS
• Write the equation.
• Substitute y by 24 and x by 16.
• Divide both sides by 24.
• Express your answer in lowest term.
• Substitute k by 2/3 and x by 12 on the equation.
• Simplify

?????? 1624?? 16 24 24?? 24 ?? 2 3 ?? 2
3 12 ??8