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Finding the Fourth Proportional to 81.55, 121.87 and 77.17

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Solution

The fourth proportional to 81.55, 121.87 and 77.17 is: 115.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.55 : 121.87 = 77.17 : x
  2. Step 2: Convert to fraction form
    81.55/121.87 = 77.17/x
  3. Step 3: Cross multiply
    81.55x = 121.87 × 77.17
  4. Step 4: Simplify right side
    81.55x = 9,404.71
  5. Step 5: Solve for x
    x = 9,404.71/81.55
  6. Step 6: Final answer
    x = 115.32

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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.