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Finding the Fourth Proportional to 81.69, 121.71 and 81.20

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Solution

The fourth proportional to 81.69, 121.71 and 81.20 is: 120.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.69 : 121.71 = 81.20 : x
  2. Step 2: Convert to fraction form
    81.69/121.71 = 81.20/x
  3. Step 3: Cross multiply
    81.69x = 121.71 × 81.20
  4. Step 4: Simplify right side
    81.69x = 9,882.24
  5. Step 5: Solve for x
    x = 9,882.24/81.69
  6. Step 6: Final answer
    x = 120.97

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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.