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Finding the Third Proportional to 642 and 1,405

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Solution

The third proportional to 642 and 1,405 is: 3,074.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    642 : 1,405 = 1,405 : x
  2. Step 2: Convert to fraction form
    642/1,405 = 1,405/x
  3. Step 3: Cross multiply
    642x = 1,405 × 1,405
  4. Step 4: Simplify right side
    642x = 1,974,025
  5. Step 5: Solve for x
    x = 1,974,025/642
  6. Step 6: Final answer
    x = 3,074.81

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Why These Related Problems?

These problems maintain the same ratio (2.19) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.