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Finding the Fourth Proportional to 81.26, 121.91 and 42.72

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Solution

The fourth proportional to 81.26, 121.91 and 42.72 is: 64.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.26 : 121.91 = 42.72 : x
  2. Step 2: Convert to fraction form
    81.26/121.91 = 42.72/x
  3. Step 3: Cross multiply
    81.26x = 121.91 × 42.72
  4. Step 4: Simplify right side
    81.26x = 5,208.00
  5. Step 5: Solve for x
    x = 5,208.00/81.26
  6. Step 6: Final answer
    x = 64.09

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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.