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Finding the Fourth Proportional to 128.76, 192.21 and 115.68

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Solution

The fourth proportional to 128.76, 192.21 and 115.68 is: 172.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.76 : 192.21 = 115.68 : x
  2. Step 2: Convert to fraction form
    128.76/192.21 = 115.68/x
  3. Step 3: Cross multiply
    128.76x = 192.21 × 115.68
  4. Step 4: Simplify right side
    128.76x = 22,234.85
  5. Step 5: Solve for x
    x = 22,234.85/128.76
  6. Step 6: Final answer
    x = 172.68

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.