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Finding the Third Proportional to 389 and 643

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Solution

The third proportional to 389 and 643 is: 1,062.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    389 : 643 = 643 : x
  2. Step 2: Convert to fraction form
    389/643 = 643/x
  3. Step 3: Cross multiply
    389x = 643 × 643
  4. Step 4: Simplify right side
    389x = 413,449
  5. Step 5: Solve for x
    x = 413,449/389
  6. Step 6: Final answer
    x = 1,062.85

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Why These Related Problems?

These problems maintain the same ratio (1.65) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.