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Finding the Third Proportional to 392 and 642.75

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Solution

The third proportional to 392 and 642.75 is: 1,053.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    392 : 642.75 = 642.75 : x
  2. Step 2: Convert to fraction form
    392/642.75 = 642.75/x
  3. Step 3: Cross multiply
    392x = 642.75 × 642.75
  4. Step 4: Simplify right side
    392x = 413,127.56
  5. Step 5: Solve for x
    x = 413,127.56/392
  6. Step 6: Final answer
    x = 1,053.90

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Why These Related Problems?

These problems maintain the same ratio (1.64) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.