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Finding the Fourth Proportional to 81.10, 121.70 and 65.91

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Solution

The fourth proportional to 81.10, 121.70 and 65.91 is: 98.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.10 : 121.70 = 65.91 : x
  2. Step 2: Convert to fraction form
    81.10/121.70 = 65.91/x
  3. Step 3: Cross multiply
    81.10x = 121.70 × 65.91
  4. Step 4: Simplify right side
    81.10x = 8,021.87
  5. Step 5: Solve for x
    x = 8,021.87/81.10
  6. Step 6: Final answer
    x = 98.91

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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.