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Finding the Fourth Proportional to 428.79, 642.89 and 220.68

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Solution

The fourth proportional to 428.79, 642.89 and 220.68 is: 330.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.79 : 642.89 = 220.68 : x
  2. Step 2: Convert to fraction form
    428.79/642.89 = 220.68/x
  3. Step 3: Cross multiply
    428.79x = 642.89 × 220.68
  4. Step 4: Simplify right side
    428.79x = 141,872.97
  5. Step 5: Solve for x
    x = 141,872.97/428.79
  6. Step 6: Final answer
    x = 330.87

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.