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Finding the Fourth Proportional to 81.78, 123.06 and 64.85

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Solution

The fourth proportional to 81.78, 123.06 and 64.85 is: 97.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.78 : 123.06 = 64.85 : x
  2. Step 2: Convert to fraction form
    81.78/123.06 = 64.85/x
  3. Step 3: Cross multiply
    81.78x = 123.06 × 64.85
  4. Step 4: Simplify right side
    81.78x = 7,980.31
  5. Step 5: Solve for x
    x = 7,980.31/81.78
  6. Step 6: Final answer
    x = 97.58

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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.