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Finding the Third Proportional to 489 and 561

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Solution

The third proportional to 489 and 561 is: 643.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    489 : 561 = 561 : x
  2. Step 2: Convert to fraction form
    489/561 = 561/x
  3. Step 3: Cross multiply
    489x = 561 × 561
  4. Step 4: Simplify right side
    489x = 314,721
  5. Step 5: Solve for x
    x = 314,721/489
  6. Step 6: Final answer
    x = 643.60

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Why These Related Problems?

These problems maintain the same ratio (1.15) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.