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Finding the Fourth Proportional to 258.62, 387.98 and 85.40

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Solution

The fourth proportional to 258.62, 387.98 and 85.40 is: 128.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.62 : 387.98 = 85.40 : x
  2. Step 2: Convert to fraction form
    258.62/387.98 = 85.40/x
  3. Step 3: Cross multiply
    258.62x = 387.98 × 85.40
  4. Step 4: Simplify right side
    258.62x = 33,134.68
  5. Step 5: Solve for x
    x = 33,134.68/258.62
  6. Step 6: Final answer
    x = 128.12

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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.