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Finding the Fourth Proportional to 90.84, 135.89 and 85.65

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Solution

The fourth proportional to 90.84, 135.89 and 85.65 is: 128.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.84 : 135.89 = 85.65 : x
  2. Step 2: Convert to fraction form
    90.84/135.89 = 85.65/x
  3. Step 3: Cross multiply
    90.84x = 135.89 × 85.65
  4. Step 4: Simplify right side
    90.84x = 11,638.98
  5. Step 5: Solve for x
    x = 11,638.98/90.84
  6. Step 6: Final answer
    x = 128.13

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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.