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Finding the Fourth Proportional to 258.91, 388.37 and 85.57

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Solution

The fourth proportional to 258.91, 388.37 and 85.57 is: 128.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.91 : 388.37 = 85.57 : x
  2. Step 2: Convert to fraction form
    258.91/388.37 = 85.57/x
  3. Step 3: Cross multiply
    258.91x = 388.37 × 85.57
  4. Step 4: Simplify right side
    258.91x = 33,233.03
  5. Step 5: Solve for x
    x = 33,233.03/258.91
  6. Step 6: Final answer
    x = 128.36

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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.