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Finding the Fourth Proportional to 258.72, 388.10 and 85.39

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Solution

The fourth proportional to 258.72, 388.10 and 85.39 is: 128.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.72 : 388.10 = 85.39 : x
  2. Step 2: Convert to fraction form
    258.72/388.10 = 85.39/x
  3. Step 3: Cross multiply
    258.72x = 388.10 × 85.39
  4. Step 4: Simplify right side
    258.72x = 33,140.86
  5. Step 5: Solve for x
    x = 33,140.86/258.72
  6. Step 6: Final answer
    x = 128.10

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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.