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Finding the Third Proportional to 639.75 and 831

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Solution

The third proportional to 639.75 and 831 is: 1,079.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.75 : 831 = 831 : x
  2. Step 2: Convert to fraction form
    639.75/831 = 831/x
  3. Step 3: Cross multiply
    639.75x = 831 × 831
  4. Step 4: Simplify right side
    639.75x = 690,561
  5. Step 5: Solve for x
    x = 690,561/639.75
  6. Step 6: Final answer
    x = 1,079.42

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Why These Related Problems?

These problems maintain the same ratio (1.30) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.