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Finding the Fourth Proportional to 86.13, 129.20 and 54

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Solution

The fourth proportional to 86.13, 129.20 and 54 is: 81

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.13 : 129.20 = 54 : x
  2. Step 2: Convert to fraction form
    86.13/129.20 = 54/x
  3. Step 3: Cross multiply
    86.13x = 129.20 × 54
  4. Step 4: Simplify right side
    86.13x = 6,976.53
  5. Step 5: Solve for x
    x = 6,976.53/86.13
  6. Step 6: Final answer
    x = 81

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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.