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Finding the Fourth Proportional to 80.61, 120.89 and 31.86

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Solution

The fourth proportional to 80.61, 120.89 and 31.86 is: 47.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    80.61 : 120.89 = 31.86 : x
  2. Step 2: Convert to fraction form
    80.61/120.89 = 31.86/x
  3. Step 3: Cross multiply
    80.61x = 120.89 × 31.86
  4. Step 4: Simplify right side
    80.61x = 3,851.40
  5. Step 5: Solve for x
    x = 3,851.40/80.61
  6. Step 6: Final answer
    x = 47.78

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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.