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Finding the Fourth Proportional to 81.15, 121.10 and 80.70

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Solution

The fourth proportional to 81.15, 121.10 and 80.70 is: 120.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.15 : 121.10 = 80.70 : x
  2. Step 2: Convert to fraction form
    81.15/121.10 = 80.70/x
  3. Step 3: Cross multiply
    81.15x = 121.10 × 80.70
  4. Step 4: Simplify right side
    81.15x = 9,772.37
  5. Step 5: Solve for x
    x = 9,772.37/81.15
  6. Step 6: Final answer
    x = 120.42

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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.