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Finding the Third Proportional to 639.50 and 989.75

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Solution

The third proportional to 639.50 and 989.75 is: 1,531.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.50 : 989.75 = 989.75 : x
  2. Step 2: Convert to fraction form
    639.50/989.75 = 989.75/x
  3. Step 3: Cross multiply
    639.50x = 989.75 × 989.75
  4. Step 4: Simplify right side
    639.50x = 979,605.06
  5. Step 5: Solve for x
    x = 979,605.06/639.50
  6. Step 6: Final answer
    x = 1,531.83

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Why These Related Problems?

These problems maintain the same ratio (1.55) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.