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Finding the Fourth Proportional to 86.44, 128.87 and 81.28

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Solution

The fourth proportional to 86.44, 128.87 and 81.28 is: 121.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.44 : 128.87 = 81.28 : x
  2. Step 2: Convert to fraction form
    86.44/128.87 = 81.28/x
  3. Step 3: Cross multiply
    86.44x = 128.87 × 81.28
  4. Step 4: Simplify right side
    86.44x = 10,474.55
  5. Step 5: Solve for x
    x = 10,474.55/86.44
  6. Step 6: Final answer
    x = 121.18

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.