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Finding the Fourth Proportional to 221.31, 305.39 and 128.09

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Solution

The fourth proportional to 221.31, 305.39 and 128.09 is: 176.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.31 : 305.39 = 128.09 : x
  2. Step 2: Convert to fraction form
    221.31/305.39 = 128.09/x
  3. Step 3: Cross multiply
    221.31x = 305.39 × 128.09
  4. Step 4: Simplify right side
    221.31x = 39,117.41
  5. Step 5: Solve for x
    x = 39,117.41/221.31
  6. Step 6: Final answer
    x = 176.75

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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.