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Finding the Fourth Proportional to 90.66, 136.08 and 85.90

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Solution

The fourth proportional to 90.66, 136.08 and 85.90 is: 128.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.66 : 136.08 = 85.90 : x
  2. Step 2: Convert to fraction form
    90.66/136.08 = 85.90/x
  3. Step 3: Cross multiply
    90.66x = 136.08 × 85.90
  4. Step 4: Simplify right side
    90.66x = 11,689.27
  5. Step 5: Solve for x
    x = 11,689.27/90.66
  6. Step 6: Final answer
    x = 128.94

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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.