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Finding the Third Proportional to 311.25 and 639

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Solution

The third proportional to 311.25 and 639 is: 1,311.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    311.25 : 639 = 639 : x
  2. Step 2: Convert to fraction form
    311.25/639 = 639/x
  3. Step 3: Cross multiply
    311.25x = 639 × 639
  4. Step 4: Simplify right side
    311.25x = 408,321
  5. Step 5: Solve for x
    x = 408,321/311.25
  6. Step 6: Final answer
    x = 1,311.87

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Why These Related Problems?

These problems maintain the same ratio (2.05) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.