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Finding the Fourth Proportional to 258.42, 387.59 and 128.39

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Solution

The fourth proportional to 258.42, 387.59 and 128.39 is: 192.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.42 : 387.59 = 128.39 : x
  2. Step 2: Convert to fraction form
    258.42/387.59 = 128.39/x
  3. Step 3: Cross multiply
    258.42x = 387.59 × 128.39
  4. Step 4: Simplify right side
    258.42x = 49,762.68
  5. Step 5: Solve for x
    x = 49,762.68/258.42
  6. Step 6: Final answer
    x = 192.57

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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.