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Finding the Fourth Proportional to 258.68, 388.09 and 85.39

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Solution

The fourth proportional to 258.68, 388.09 and 85.39 is: 128.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.68 : 388.09 = 85.39 : x
  2. Step 2: Convert to fraction form
    258.68/388.09 = 85.39/x
  3. Step 3: Cross multiply
    258.68x = 388.09 × 85.39
  4. Step 4: Simplify right side
    258.68x = 33,138.14
  5. Step 5: Solve for x
    x = 33,138.14/258.68
  6. Step 6: Final answer
    x = 128.11

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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.