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Finding the Fourth Proportional to 221.40, 305.50 and 128.12

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Solution

The fourth proportional to 221.40, 305.50 and 128.12 is: 176.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    221.40 : 305.50 = 128.12 : x
  2. Step 2: Convert to fraction form
    221.40/305.50 = 128.12/x
  3. Step 3: Cross multiply
    221.40x = 305.50 × 128.12
  4. Step 4: Simplify right side
    221.40x = 39,140.66
  5. Step 5: Solve for x
    x = 39,140.66/221.40
  6. Step 6: Final answer
    x = 176.79

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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.