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Finding the Fourth Proportional to 128.97, 177.92 and 87.55

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Solution

The fourth proportional to 128.97, 177.92 and 87.55 is: 120.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.97 : 177.92 = 87.55 : x
  2. Step 2: Convert to fraction form
    128.97/177.92 = 87.55/x
  3. Step 3: Cross multiply
    128.97x = 177.92 × 87.55
  4. Step 4: Simplify right side
    128.97x = 15,576.90
  5. Step 5: Solve for x
    x = 15,576.90/128.97
  6. Step 6: Final answer
    x = 120.78

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.