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Finding the Fourth Proportional to 81.50, 111.66 and 78.42

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Solution

The fourth proportional to 81.50, 111.66 and 78.42 is: 107.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.50 : 111.66 = 78.42 : x
  2. Step 2: Convert to fraction form
    81.50/111.66 = 78.42/x
  3. Step 3: Cross multiply
    81.50x = 111.66 × 78.42
  4. Step 4: Simplify right side
    81.50x = 8,756.61
  5. Step 5: Solve for x
    x = 8,756.61/81.50
  6. Step 6: Final answer
    x = 107.44

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.