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Finding the Third Proportional to 311.81 and 638.91

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Solution

The third proportional to 311.81 and 638.91 is: 1,309.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    311.81 : 638.91 = 638.91 : x
  2. Step 2: Convert to fraction form
    311.81/638.91 = 638.91/x
  3. Step 3: Cross multiply
    311.81x = 638.91 × 638.91
  4. Step 4: Simplify right side
    311.81x = 408,201.20
  5. Step 5: Solve for x
    x = 408,201.20/311.81
  6. Step 6: Final answer
    x = 1,309.12

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Why These Related Problems?

These problems maintain the same ratio (2.05) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.