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Finding the Fourth Proportional to 128.12, 192.18 and 81.23

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Solution

The fourth proportional to 128.12, 192.18 and 81.23 is: 121.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.12 : 192.18 = 81.23 : x
  2. Step 2: Convert to fraction form
    128.12/192.18 = 81.23/x
  3. Step 3: Cross multiply
    128.12x = 192.18 × 81.23
  4. Step 4: Simplify right side
    128.12x = 15,610.78
  5. Step 5: Solve for x
    x = 15,610.78/128.12
  6. Step 6: Final answer
    x = 121.85

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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.