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Finding the Fourth Proportional to 258.36, 387.58 and 128.43

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Solution

The fourth proportional to 258.36, 387.58 and 128.43 is: 192.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    258.36 : 387.58 = 128.43 : x
  2. Step 2: Convert to fraction form
    258.36/387.58 = 128.43/x
  3. Step 3: Cross multiply
    258.36x = 387.58 × 128.43
  4. Step 4: Simplify right side
    258.36x = 49,776.26
  5. Step 5: Solve for x
    x = 49,776.26/258.36
  6. Step 6: Final answer
    x = 192.66

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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.