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Finding the Fourth Proportional to 81.66, 122.40 and 61.31

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Solution

The fourth proportional to 81.66, 122.40 and 61.31 is: 91.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.66 : 122.40 = 61.31 : x
  2. Step 2: Convert to fraction form
    81.66/122.40 = 61.31/x
  3. Step 3: Cross multiply
    81.66x = 122.40 × 61.31
  4. Step 4: Simplify right side
    81.66x = 7,504.19
  5. Step 5: Solve for x
    x = 7,504.19/81.66
  6. Step 6: Final answer
    x = 91.90

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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.