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Finding the Third Proportional to 639 and 915

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Solution

The third proportional to 639 and 915 is: 1,310.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    639 : 915 = 915 : x
  2. Step 2: Convert to fraction form
    639/915 = 915/x
  3. Step 3: Cross multiply
    639x = 915 × 915
  4. Step 4: Simplify right side
    639x = 837,225
  5. Step 5: Solve for x
    x = 837,225/639
  6. Step 6: Final answer
    x = 1,310.21

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Why These Related Problems?

These problems maintain the same ratio (1.43) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.