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Finding the Fourth Proportional to 86.38, 128.85 and 79.92

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Solution

The fourth proportional to 86.38, 128.85 and 79.92 is: 119.22

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.38 : 128.85 = 79.92 : x
  2. Step 2: Convert to fraction form
    86.38/128.85 = 79.92/x
  3. Step 3: Cross multiply
    86.38x = 128.85 × 79.92
  4. Step 4: Simplify right side
    86.38x = 10,297.69
  5. Step 5: Solve for x
    x = 10,297.69/86.38
  6. Step 6: Final answer
    x = 119.22

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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.