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Finding the Fourth Proportional to 221.47, 305.61 and 128.20

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Solution

The fourth proportional to 221.47, 305.61 and 128.20 is: 176.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.47 : 305.61 = 128.20 : x
  2. Step 2: Convert to fraction form
    221.47/305.61 = 128.20/x
  3. Step 3: Cross multiply
    221.47x = 305.61 × 128.20
  4. Step 4: Simplify right side
    221.47x = 39,179.20
  5. Step 5: Solve for x
    x = 39,179.20/221.47
  6. Step 6: Final answer
    x = 176.91

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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.