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Finding the Third Proportional to 391.31 and 687.38

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Solution

The third proportional to 391.31 and 687.38 is: 1,207.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    391.31 : 687.38 = 687.38 : x
  2. Step 2: Convert to fraction form
    391.31/687.38 = 687.38/x
  3. Step 3: Cross multiply
    391.31x = 687.38 × 687.38
  4. Step 4: Simplify right side
    391.31x = 472,484.39
  5. Step 5: Solve for x
    x = 472,484.39/391.31
  6. Step 6: Final answer
    x = 1,207.43

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Why These Related Problems?

These problems maintain the same ratio (1.76) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.