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Finding the Fourth Proportional to 221.50, 305.64 and 128.20

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Solution

The fourth proportional to 221.50, 305.64 and 128.20 is: 176.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.50 : 305.64 = 128.20 : x
  2. Step 2: Convert to fraction form
    221.50/305.64 = 128.20/x
  3. Step 3: Cross multiply
    221.50x = 305.64 × 128.20
  4. Step 4: Simplify right side
    221.50x = 39,183.05
  5. Step 5: Solve for x
    x = 39,183.05/221.50
  6. Step 6: Final answer
    x = 176.90

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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.