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Finding the Fourth Proportional to 90.40, 135.56 and 85.40

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Solution

The fourth proportional to 90.40, 135.56 and 85.40 is: 128.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.40 : 135.56 = 85.40 : x
  2. Step 2: Convert to fraction form
    90.40/135.56 = 85.40/x
  3. Step 3: Cross multiply
    90.40x = 135.56 × 85.40
  4. Step 4: Simplify right side
    90.40x = 11,576.82
  5. Step 5: Solve for x
    x = 11,576.82/90.40
  6. Step 6: Final answer
    x = 128.06

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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.