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Finding the Fourth Proportional to 90.78, 136.20 and 54.74

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Solution

The fourth proportional to 90.78, 136.20 and 54.74 is: 82.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.78 : 136.20 = 54.74 : x
  2. Step 2: Convert to fraction form
    90.78/136.20 = 54.74/x
  3. Step 3: Cross multiply
    90.78x = 136.20 × 54.74
  4. Step 4: Simplify right side
    90.78x = 7,455.59
  5. Step 5: Solve for x
    x = 7,455.59/90.78
  6. Step 6: Final answer
    x = 82.13

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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.