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Finding the Fourth Proportional to 81.47, 122.18 and 42.90

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Solution

The fourth proportional to 81.47, 122.18 and 42.90 is: 64.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.47 : 122.18 = 42.90 : x
  2. Step 2: Convert to fraction form
    81.47/122.18 = 42.90/x
  3. Step 3: Cross multiply
    81.47x = 122.18 × 42.90
  4. Step 4: Simplify right side
    81.47x = 5,240.85
  5. Step 5: Solve for x
    x = 5,240.85/81.47
  6. Step 6: Final answer
    x = 64.33

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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.