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Finding the Fourth Proportional to 218.78, 328.11 and 81.89

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Solution

The fourth proportional to 218.78, 328.11 and 81.89 is: 122.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    218.78 : 328.11 = 81.89 : x
  2. Step 2: Convert to fraction form
    218.78/328.11 = 81.89/x
  3. Step 3: Cross multiply
    218.78x = 328.11 × 81.89
  4. Step 4: Simplify right side
    218.78x = 26,868.93
  5. Step 5: Solve for x
    x = 26,868.93/218.78
  6. Step 6: Final answer
    x = 122.81

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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.