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Finding the Fourth Proportional to 90.78, 136.18 and 66.90

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Solution

The fourth proportional to 90.78, 136.18 and 66.90 is: 100.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.78 : 136.18 = 66.90 : x
  2. Step 2: Convert to fraction form
    90.78/136.18 = 66.90/x
  3. Step 3: Cross multiply
    90.78x = 136.18 × 66.90
  4. Step 4: Simplify right side
    90.78x = 9,110.44
  5. Step 5: Solve for x
    x = 9,110.44/90.78
  6. Step 6: Final answer
    x = 100.36

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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.