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Finding the Fourth Proportional to 81.25, 121.78 and 80.87

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Solution

The fourth proportional to 81.25, 121.78 and 80.87 is: 121.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.25 : 121.78 = 80.87 : x
  2. Step 2: Convert to fraction form
    81.25/121.78 = 80.87/x
  3. Step 3: Cross multiply
    81.25x = 121.78 × 80.87
  4. Step 4: Simplify right side
    81.25x = 9,847.84
  5. Step 5: Solve for x
    x = 9,847.84/81.25
  6. Step 6: Final answer
    x = 121.21

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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.