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Finding the Fourth Proportional to 639.72, 961.20 and 408.72

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Solution

The fourth proportional to 639.72, 961.20 and 408.72 is: 614.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.72 : 961.20 = 408.72 : x
  2. Step 2: Convert to fraction form
    639.72/961.20 = 408.72/x
  3. Step 3: Cross multiply
    639.72x = 961.20 × 408.72
  4. Step 4: Simplify right side
    639.72x = 392,861.66
  5. Step 5: Solve for x
    x = 392,861.66/639.72
  6. Step 6: Final answer
    x = 614.12

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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.