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Finding the Fourth Proportional to 128.34, 192.39 and 76.91

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Solution

The fourth proportional to 128.34, 192.39 and 76.91 is: 115.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.34 : 192.39 = 76.91 : x
  2. Step 2: Convert to fraction form
    128.34/192.39 = 76.91/x
  3. Step 3: Cross multiply
    128.34x = 192.39 × 76.91
  4. Step 4: Simplify right side
    128.34x = 14,795.75
  5. Step 5: Solve for x
    x = 14,795.75/128.34
  6. Step 6: Final answer
    x = 115.29

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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.