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Finding the Fourth Proportional to 128.10, 192.42 and 76.85

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Solution

The fourth proportional to 128.10, 192.42 and 76.85 is: 115.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.10 : 192.42 = 76.85 : x
  2. Step 2: Convert to fraction form
    128.10/192.42 = 76.85/x
  3. Step 3: Cross multiply
    128.10x = 192.42 × 76.85
  4. Step 4: Simplify right side
    128.10x = 14,786.51
  5. Step 5: Solve for x
    x = 14,786.51/128.10
  6. Step 6: Final answer
    x = 115.43

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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.