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Finding the Fourth Proportional to 86.81, 129.53 and 81.61

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Solution

The fourth proportional to 86.81, 129.53 and 81.61 is: 121.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.81 : 129.53 = 81.61 : x
  2. Step 2: Convert to fraction form
    86.81/129.53 = 81.61/x
  3. Step 3: Cross multiply
    86.81x = 129.53 × 81.61
  4. Step 4: Simplify right side
    86.81x = 10,570.82
  5. Step 5: Solve for x
    x = 10,570.82/86.81
  6. Step 6: Final answer
    x = 121.78

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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.