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Finding the Fourth Proportional to 86.07, 128.36 and 81.28

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Solution

The fourth proportional to 86.07, 128.36 and 81.28 is: 121.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.07 : 128.36 = 81.28 : x
  2. Step 2: Convert to fraction form
    86.07/128.36 = 81.28/x
  3. Step 3: Cross multiply
    86.07x = 128.36 × 81.28
  4. Step 4: Simplify right side
    86.07x = 10,432.37
  5. Step 5: Solve for x
    x = 10,432.37/86.07
  6. Step 6: Final answer
    x = 121.21

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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.