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Finding the Third Proportional to 421.31 and 639.56

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Solution

The third proportional to 421.31 and 639.56 is: 970.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.31 : 639.56 = 639.56 : x
  2. Step 2: Convert to fraction form
    421.31/639.56 = 639.56/x
  3. Step 3: Cross multiply
    421.31x = 639.56 × 639.56
  4. Step 4: Simplify right side
    421.31x = 409,040.19
  5. Step 5: Solve for x
    x = 409,040.19/421.31
  6. Step 6: Final answer
    x = 970.87

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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.