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Finding the Fourth Proportional to 86.10, 128.85 and 81.11

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Solution

The fourth proportional to 86.10, 128.85 and 81.11 is: 121.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.10 : 128.85 = 81.11 : x
  2. Step 2: Convert to fraction form
    86.10/128.85 = 81.11/x
  3. Step 3: Cross multiply
    86.10x = 128.85 × 81.11
  4. Step 4: Simplify right side
    86.10x = 10,451.00
  5. Step 5: Solve for x
    x = 10,451.00/86.10
  6. Step 6: Final answer
    x = 121.38

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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.