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Finding the Third Proportional to 687 and 921

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Solution

The third proportional to 687 and 921 is: 1,234.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    687 : 921 = 921 : x
  2. Step 2: Convert to fraction form
    687/921 = 921/x
  3. Step 3: Cross multiply
    687x = 921 × 921
  4. Step 4: Simplify right side
    687x = 848,241
  5. Step 5: Solve for x
    x = 848,241/687
  6. Step 6: Final answer
    x = 1,234.70

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Why These Related Problems?

These problems maintain the same ratio (1.34) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.