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Finding the Fourth Proportional to 686.69, 1,029.90 and 439.78

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Solution

The fourth proportional to 686.69, 1,029.90 and 439.78 is: 659.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    686.69 : 1,029.90 = 439.78 : x
  2. Step 2: Convert to fraction form
    686.69/1,029.90 = 439.78/x
  3. Step 3: Cross multiply
    686.69x = 1,029.90 × 439.78
  4. Step 4: Simplify right side
    686.69x = 452,929.42
  5. Step 5: Solve for x
    x = 452,929.42/686.69
  6. Step 6: Final answer
    x = 659.58

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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.