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Finding the Fourth Proportional to 90.92, 137.09 and 85.72

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Solution

The fourth proportional to 90.92, 137.09 and 85.72 is: 129.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.92 : 137.09 = 85.72 : x
  2. Step 2: Convert to fraction form
    90.92/137.09 = 85.72/x
  3. Step 3: Cross multiply
    90.92x = 137.09 × 85.72
  4. Step 4: Simplify right side
    90.92x = 11,751.35
  5. Step 5: Solve for x
    x = 11,751.35/90.92
  6. Step 6: Final answer
    x = 129.25

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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.