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Finding the Fourth Proportional to 85.30, 128.22 and 76.78

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Solution

The fourth proportional to 85.30, 128.22 and 76.78 is: 115.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.30 : 128.22 = 76.78 : x
  2. Step 2: Convert to fraction form
    85.30/128.22 = 76.78/x
  3. Step 3: Cross multiply
    85.30x = 128.22 × 76.78
  4. Step 4: Simplify right side
    85.30x = 9,844.73
  5. Step 5: Solve for x
    x = 9,844.73/85.30
  6. Step 6: Final answer
    x = 115.41

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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.