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Finding the Fourth Proportional to 258.93, 387.90 and 128.78

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Solution

The fourth proportional to 258.93, 387.90 and 128.78 is: 192.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.93 : 387.90 = 128.78 : x
  2. Step 2: Convert to fraction form
    258.93/387.90 = 128.78/x
  3. Step 3: Cross multiply
    258.93x = 387.90 × 128.78
  4. Step 4: Simplify right side
    258.93x = 49,951.82
  5. Step 5: Solve for x
    x = 49,951.82/258.93
  6. Step 6: Final answer
    x = 192.92

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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.