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Finding the Fourth Proportional to 120.39, 180.40 and 81.89

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Solution

The fourth proportional to 120.39, 180.40 and 81.89 is: 122.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.39 : 180.40 = 81.89 : x
  2. Step 2: Convert to fraction form
    120.39/180.40 = 81.89/x
  3. Step 3: Cross multiply
    120.39x = 180.40 × 81.89
  4. Step 4: Simplify right side
    120.39x = 14,772.96
  5. Step 5: Solve for x
    x = 14,772.96/120.39
  6. Step 6: Final answer
    x = 122.71

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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.