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Finding the Third Proportional to 639 and 840

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Solution

The third proportional to 639 and 840 is: 1,104.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    639 : 840 = 840 : x
  2. Step 2: Convert to fraction form
    639/840 = 840/x
  3. Step 3: Cross multiply
    639x = 840 × 840
  4. Step 4: Simplify right side
    639x = 705,600
  5. Step 5: Solve for x
    x = 705,600/639
  6. Step 6: Final answer
    x = 1,104.23

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Why These Related Problems?

These problems maintain the same ratio (1.31) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.