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Finding the Fourth Proportional to 81.87, 121.98 and 81.08

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Solution

The fourth proportional to 81.87, 121.98 and 81.08 is: 120.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.87 : 121.98 = 81.08 : x
  2. Step 2: Convert to fraction form
    81.87/121.98 = 81.08/x
  3. Step 3: Cross multiply
    81.87x = 121.98 × 81.08
  4. Step 4: Simplify right side
    81.87x = 9,890.98
  5. Step 5: Solve for x
    x = 9,890.98/81.87
  6. Step 6: Final answer
    x = 120.82

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.