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Finding the Third Proportional to 399 and 638.50

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Solution

The third proportional to 399 and 638.50 is: 1,021.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    399 : 638.50 = 638.50 : x
  2. Step 2: Convert to fraction form
    399/638.50 = 638.50/x
  3. Step 3: Cross multiply
    399x = 638.50 × 638.50
  4. Step 4: Simplify right side
    399x = 407,682.25
  5. Step 5: Solve for x
    x = 407,682.25/399
  6. Step 6: Final answer
    x = 1,021.76

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Why These Related Problems?

These problems maintain the same ratio (1.60) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.