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Finding the Fourth Proportional to 81.24, 121.72 and 69.78

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Solution

The fourth proportional to 81.24, 121.72 and 69.78 is: 104.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.24 : 121.72 = 69.78 : x
  2. Step 2: Convert to fraction form
    81.24/121.72 = 69.78/x
  3. Step 3: Cross multiply
    81.24x = 121.72 × 69.78
  4. Step 4: Simplify right side
    81.24x = 8,493.62
  5. Step 5: Solve for x
    x = 8,493.62/81.24
  6. Step 6: Final answer
    x = 104.55

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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.