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Finding the Fourth Proportional to 120.55, 180.71 and 81.91

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Solution

The fourth proportional to 120.55, 180.71 and 81.91 is: 122.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.55 : 180.71 = 81.91 : x
  2. Step 2: Convert to fraction form
    120.55/180.71 = 81.91/x
  3. Step 3: Cross multiply
    120.55x = 180.71 × 81.91
  4. Step 4: Simplify right side
    120.55x = 14,801.86
  5. Step 5: Solve for x
    x = 14,801.86/120.55
  6. Step 6: Final answer
    x = 122.78

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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.