Example

Finding the Inverse Variation Equation Given y=20y = 20 When x=8x = 8

Problem: If yy varies inversely with xx and y=20y = 20 when x=8x = 8, find the equation that relates xx and yy.

Step 1 — Write the inverse variation formula: y=kxy = \frac{k}{x}

Step 2 — Substitute the given values: Replace yy with 2020 and xx with 88: 20=k820 = \frac{k}{8}

Step 3 — Solve for the constant of variation: Multiply both sides by 88: 820=8k88 \cdot 20 = 8 \cdot \frac{k}{8} 160=k160 = k

Step 4 — Write the equation: Substitute k=160k = 160 back into the general formula: y=160xy = \frac{160}{x}

The equation relating xx and yy is y=160xy = \frac{160}{x}.

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Updated 2026-04-21

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