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Finding the Fourth Proportional to 81.31, 121.69 and 72.31

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Solution

The fourth proportional to 81.31, 121.69 and 72.31 is: 108.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.31 : 121.69 = 72.31 : x
  2. Step 2: Convert to fraction form
    81.31/121.69 = 72.31/x
  3. Step 3: Cross multiply
    81.31x = 121.69 × 72.31
  4. Step 4: Simplify right side
    81.31x = 8,799.40
  5. Step 5: Solve for x
    x = 8,799.40/81.31
  6. Step 6: Final answer
    x = 108.22

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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.