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Finding the Fourth Proportional to 221.89, 306.21 and 128.65

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Solution

The fourth proportional to 221.89, 306.21 and 128.65 is: 177.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.89 : 306.21 = 128.65 : x
  2. Step 2: Convert to fraction form
    221.89/306.21 = 128.65/x
  3. Step 3: Cross multiply
    221.89x = 306.21 × 128.65
  4. Step 4: Simplify right side
    221.89x = 39,393.92
  5. Step 5: Solve for x
    x = 39,393.92/221.89
  6. Step 6: Final answer
    x = 177.54

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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.