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Finding the Fourth Proportional to 686.72, 1,029.75 and 321.20

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Solution

The fourth proportional to 686.72, 1,029.75 and 321.20 is: 481.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.72 : 1,029.75 = 321.20 : x
  2. Step 2: Convert to fraction form
    686.72/1,029.75 = 321.20/x
  3. Step 3: Cross multiply
    686.72x = 1,029.75 × 321.20
  4. Step 4: Simplify right side
    686.72x = 330,755.70
  5. Step 5: Solve for x
    x = 330,755.70/686.72
  6. Step 6: Final answer
    x = 481.65

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.