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Finding the Third Proportional to 643 and 1,387

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Solution

The third proportional to 643 and 1,387 is: 2,991.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    643 : 1,387 = 1,387 : x
  2. Step 2: Convert to fraction form
    643/1,387 = 1,387/x
  3. Step 3: Cross multiply
    643x = 1,387 × 1,387
  4. Step 4: Simplify right side
    643x = 1,923,769
  5. Step 5: Solve for x
    x = 1,923,769/643
  6. Step 6: Final answer
    x = 2,991.86

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Why These Related Problems?

These problems maintain the same ratio (2.16) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.