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Finding the Fourth Proportional to 120.21, 180.39 and 85.89

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Solution

The fourth proportional to 120.21, 180.39 and 85.89 is: 128.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.21 : 180.39 = 85.89 : x
  2. Step 2: Convert to fraction form
    120.21/180.39 = 85.89/x
  3. Step 3: Cross multiply
    120.21x = 180.39 × 85.89
  4. Step 4: Simplify right side
    120.21x = 15,493.70
  5. Step 5: Solve for x
    x = 15,493.70/120.21
  6. Step 6: Final answer
    x = 128.89

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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.