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Finding the Fourth Proportional to 258.78, 389.16 and 206.85

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Solution

The fourth proportional to 258.78, 389.16 and 206.85 is: 311.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.78 : 389.16 = 206.85 : x
  2. Step 2: Convert to fraction form
    258.78/389.16 = 206.85/x
  3. Step 3: Cross multiply
    258.78x = 389.16 × 206.85
  4. Step 4: Simplify right side
    258.78x = 80,497.75
  5. Step 5: Solve for x
    x = 80,497.75/258.78
  6. Step 6: Final answer
    x = 311.07

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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.