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Finding the Fourth Proportional to 221.91, 306.30 and 128.72

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Solution

The fourth proportional to 221.91, 306.30 and 128.72 is: 177.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.91 : 306.30 = 128.72 : x
  2. Step 2: Convert to fraction form
    221.91/306.30 = 128.72/x
  3. Step 3: Cross multiply
    221.91x = 306.30 × 128.72
  4. Step 4: Simplify right side
    221.91x = 39,425.40
  5. Step 5: Solve for x
    x = 39,425.40/221.91
  6. Step 6: Final answer
    x = 177.66

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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.