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Finding the Fourth Proportional to 81, 120.78 and 72.41

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Solution

The fourth proportional to 81, 120.78 and 72.41 is: 107.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    81 : 120.78 = 72.41 : x
  2. Step 2: Convert to fraction form
    81/120.78 = 72.41/x
  3. Step 3: Cross multiply
    81x = 120.78 × 72.41
  4. Step 4: Simplify right side
    81x = 8,745.08
  5. Step 5: Solve for x
    x = 8,745.08/81
  6. Step 6: Final answer
    x = 107.96

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.