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Finding the Fourth Proportional to 86.13, 128.91 and 51.81

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Solution

The fourth proportional to 86.13, 128.91 and 51.81 is: 77.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.13 : 128.91 = 51.81 : x
  2. Step 2: Convert to fraction form
    86.13/128.91 = 51.81/x
  3. Step 3: Cross multiply
    86.13x = 128.91 × 51.81
  4. Step 4: Simplify right side
    86.13x = 6,678.83
  5. Step 5: Solve for x
    x = 6,678.83/86.13
  6. Step 6: Final answer
    x = 77.54

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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.