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Finding the Fourth Proportional to 90.87, 136.32 and 80.78

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Solution

The fourth proportional to 90.87, 136.32 and 80.78 is: 121.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.87 : 136.32 = 80.78 : x
  2. Step 2: Convert to fraction form
    90.87/136.32 = 80.78/x
  3. Step 3: Cross multiply
    90.87x = 136.32 × 80.78
  4. Step 4: Simplify right side
    90.87x = 11,011.25
  5. Step 5: Solve for x
    x = 11,011.25/90.87
  6. Step 6: Final answer
    x = 121.18

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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.