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Finding the Fourth Proportional to 85.22, 128.46 and 76.85

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Solution

The fourth proportional to 85.22, 128.46 and 76.85 is: 115.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.22 : 128.46 = 76.85 : x
  2. Step 2: Convert to fraction form
    85.22/128.46 = 76.85/x
  3. Step 3: Cross multiply
    85.22x = 128.46 × 76.85
  4. Step 4: Simplify right side
    85.22x = 9,872.15
  5. Step 5: Solve for x
    x = 9,872.15/85.22
  6. Step 6: Final answer
    x = 115.84

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.