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Finding the Fourth Proportional to 258.48, 387.78 and 85.11

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Solution

The fourth proportional to 258.48, 387.78 and 85.11 is: 127.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.48 : 387.78 = 85.11 : x
  2. Step 2: Convert to fraction form
    258.48/387.78 = 85.11/x
  3. Step 3: Cross multiply
    258.48x = 387.78 × 85.11
  4. Step 4: Simplify right side
    258.48x = 33,003.96
  5. Step 5: Solve for x
    x = 33,003.96/258.48
  6. Step 6: Final answer
    x = 127.68

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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.