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Finding the Fourth Proportional to 90.99, 136.55 and 85.71

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Solution

The fourth proportional to 90.99, 136.55 and 85.71 is: 128.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.99 : 136.55 = 85.71 : x
  2. Step 2: Convert to fraction form
    90.99/136.55 = 85.71/x
  3. Step 3: Cross multiply
    90.99x = 136.55 × 85.71
  4. Step 4: Simplify right side
    90.99x = 11,703.27
  5. Step 5: Solve for x
    x = 11,703.27/90.99
  6. Step 6: Final answer
    x = 128.62

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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.