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Finding the Fourth Proportional to 81.90, 122.80 and 30.58

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Solution

The fourth proportional to 81.90, 122.80 and 30.58 is: 45.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.90 : 122.80 = 30.58 : x
  2. Step 2: Convert to fraction form
    81.90/122.80 = 30.58/x
  3. Step 3: Cross multiply
    81.90x = 122.80 × 30.58
  4. Step 4: Simplify right side
    81.90x = 3,755.03
  5. Step 5: Solve for x
    x = 3,755.03/81.90
  6. Step 6: Final answer
    x = 45.85

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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.