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Finding the Fourth Proportional to 86.81, 129.35 and 81.56

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Solution

The fourth proportional to 86.81, 129.35 and 81.56 is: 121.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.81 : 129.35 = 81.56 : x
  2. Step 2: Convert to fraction form
    86.81/129.35 = 81.56/x
  3. Step 3: Cross multiply
    86.81x = 129.35 × 81.56
  4. Step 4: Simplify right side
    86.81x = 10,550.31
  5. Step 5: Solve for x
    x = 10,550.31/86.81
  6. Step 6: Final answer
    x = 121.54

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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.