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Finding the Third Proportional to 420 and 639

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Solution

The third proportional to 420 and 639 is: 972.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    420 : 639 = 639 : x
  2. Step 2: Convert to fraction form
    420/639 = 639/x
  3. Step 3: Cross multiply
    420x = 639 × 639
  4. Step 4: Simplify right side
    420x = 408,321
  5. Step 5: Solve for x
    x = 408,321/420
  6. Step 6: Final answer
    x = 972.19

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Why These Related Problems?

These problems maintain the same ratio (1.52) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.