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Finding the Fourth Proportional to 428.78, 643.17 and 120.65

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Solution

The fourth proportional to 428.78, 643.17 and 120.65 is: 180.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.78 : 643.17 = 120.65 : x
  2. Step 2: Convert to fraction form
    428.78/643.17 = 120.65/x
  3. Step 3: Cross multiply
    428.78x = 643.17 × 120.65
  4. Step 4: Simplify right side
    428.78x = 77,595.70
  5. Step 5: Solve for x
    x = 77,595.70/428.78
  6. Step 6: Final answer
    x = 180.97

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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.