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Finding the Fourth Proportional to 128.72, 192.90 and 80.66

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Solution

The fourth proportional to 128.72, 192.90 and 80.66 is: 120.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.72 : 192.90 = 80.66 : x
  2. Step 2: Convert to fraction form
    128.72/192.90 = 80.66/x
  3. Step 3: Cross multiply
    128.72x = 192.90 × 80.66
  4. Step 4: Simplify right side
    128.72x = 15,559.31
  5. Step 5: Solve for x
    x = 15,559.31/128.72
  6. Step 6: Final answer
    x = 120.88

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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.