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Finding the Fourth Proportional to 221.91, 306.20 and 128.58

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Solution

The fourth proportional to 221.91, 306.20 and 128.58 is: 177.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.91 : 306.20 = 128.58 : x
  2. Step 2: Convert to fraction form
    221.91/306.20 = 128.58/x
  3. Step 3: Cross multiply
    221.91x = 306.20 × 128.58
  4. Step 4: Simplify right side
    221.91x = 39,371.52
  5. Step 5: Solve for x
    x = 39,371.52/221.91
  6. Step 6: Final answer
    x = 177.42

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.