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Finding the Fourth Proportional to 91.20, 136.92 and 85.92

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Solution

The fourth proportional to 91.20, 136.92 and 85.92 is: 128.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.20 : 136.92 = 85.92 : x
  2. Step 2: Convert to fraction form
    91.20/136.92 = 85.92/x
  3. Step 3: Cross multiply
    91.20x = 136.92 × 85.92
  4. Step 4: Simplify right side
    91.20x = 11,764.17
  5. Step 5: Solve for x
    x = 11,764.17/91.20
  6. Step 6: Final answer
    x = 128.99

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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.