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Finding the Fourth Proportional to 81.15, 111.90 and 77.13

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Solution

The fourth proportional to 81.15, 111.90 and 77.13 is: 106.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.15 : 111.90 = 77.13 : x
  2. Step 2: Convert to fraction form
    81.15/111.90 = 77.13/x
  3. Step 3: Cross multiply
    81.15x = 111.90 × 77.13
  4. Step 4: Simplify right side
    81.15x = 8,630.85
  5. Step 5: Solve for x
    x = 8,630.85/81.15
  6. Step 6: Final answer
    x = 106.36

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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.