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Finding the Fourth Proportional to 221.45, 305.57 and 128.21

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Solution

The fourth proportional to 221.45, 305.57 and 128.21 is: 176.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.45 : 305.57 = 128.21 : x
  2. Step 2: Convert to fraction form
    221.45/305.57 = 128.21/x
  3. Step 3: Cross multiply
    221.45x = 305.57 × 128.21
  4. Step 4: Simplify right side
    221.45x = 39,175.92
  5. Step 5: Solve for x
    x = 39,175.92/221.45
  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.