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Finding the Third Proportional to 644.25 and 690.38

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Solution

The third proportional to 644.25 and 690.38 is: 739.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    644.25 : 690.38 = 690.38 : x
  2. Step 2: Convert to fraction form
    644.25/690.38 = 690.38/x
  3. Step 3: Cross multiply
    644.25x = 690.38 × 690.38
  4. Step 4: Simplify right side
    644.25x = 476,617.64
  5. Step 5: Solve for x
    x = 476,617.64/644.25
  6. Step 6: Final answer
    x = 739.80

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Why These Related Problems?

These problems maintain the same ratio (1.07) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.