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Finding the Fourth Proportional to 258.54, 387.82 and 85.21

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Solution

The fourth proportional to 258.54, 387.82 and 85.21 is: 127.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.54 : 387.82 = 85.21 : x
  2. Step 2: Convert to fraction form
    258.54/387.82 = 85.21/x
  3. Step 3: Cross multiply
    258.54x = 387.82 × 85.21
  4. Step 4: Simplify right side
    258.54x = 33,047.32
  5. Step 5: Solve for x
    x = 33,047.32/258.54
  6. Step 6: Final answer
    x = 127.82

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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.