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Finding the Fourth Proportional to 81.20, 112.20 and 61.76

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Solution

The fourth proportional to 81.20, 112.20 and 61.76 is: 85.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.20 : 112.20 = 61.76 : x
  2. Step 2: Convert to fraction form
    81.20/112.20 = 61.76/x
  3. Step 3: Cross multiply
    81.20x = 112.20 × 61.76
  4. Step 4: Simplify right side
    81.20x = 6,929.47
  5. Step 5: Solve for x
    x = 6,929.47/81.20
  6. Step 6: Final answer
    x = 85.34

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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.