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Finding the Fourth Proportional to 81.98, 113.19 and 65.78

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Solution

The fourth proportional to 81.98, 113.19 and 65.78 is: 90.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.98 : 113.19 = 65.78 : x
  2. Step 2: Convert to fraction form
    81.98/113.19 = 65.78/x
  3. Step 3: Cross multiply
    81.98x = 113.19 × 65.78
  4. Step 4: Simplify right side
    81.98x = 7,445.64
  5. Step 5: Solve for x
    x = 7,445.64/81.98
  6. Step 6: Final answer
    x = 90.82

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.