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Finding the Fourth Proportional to 81.40, 122.20 and 77.72

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Solution

The fourth proportional to 81.40, 122.20 and 77.72 is: 116.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.40 : 122.20 = 77.72 : x
  2. Step 2: Convert to fraction form
    81.40/122.20 = 77.72/x
  3. Step 3: Cross multiply
    81.40x = 122.20 × 77.72
  4. Step 4: Simplify right side
    81.40x = 9,497.38
  5. Step 5: Solve for x
    x = 9,497.38/81.40
  6. Step 6: Final answer
    x = 116.68

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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.