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Finding the Fourth Proportional to 221.72, 305.94 and 128.39

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Solution

The fourth proportional to 221.72, 305.94 and 128.39 is: 177.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.72 : 305.94 = 128.39 : x
  2. Step 2: Convert to fraction form
    221.72/305.94 = 128.39/x
  3. Step 3: Cross multiply
    221.72x = 305.94 × 128.39
  4. Step 4: Simplify right side
    221.72x = 39,280.31
  5. Step 5: Solve for x
    x = 39,280.31/221.72
  6. Step 6: Final answer
    x = 177.16

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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.