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Finding the Fourth Proportional to 81.64, 121.85 and 71.38

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Solution

The fourth proportional to 81.64, 121.85 and 71.38 is: 106.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.64 : 121.85 = 71.38 : x
  2. Step 2: Convert to fraction form
    81.64/121.85 = 71.38/x
  3. Step 3: Cross multiply
    81.64x = 121.85 × 71.38
  4. Step 4: Simplify right side
    81.64x = 8,697.65
  5. Step 5: Solve for x
    x = 8,697.65/81.64
  6. Step 6: Final answer
    x = 106.54

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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.