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Finding the Third Proportional to 640.50 and 690.75

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Solution

The third proportional to 640.50 and 690.75 is: 744.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    640.50 : 690.75 = 690.75 : x
  2. Step 2: Convert to fraction form
    640.50/690.75 = 690.75/x
  3. Step 3: Cross multiply
    640.50x = 690.75 × 690.75
  4. Step 4: Simplify right side
    640.50x = 477,135.56
  5. Step 5: Solve for x
    x = 477,135.56/640.50
  6. Step 6: Final answer
    x = 744.94

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Why These Related Problems?

These problems maintain the same ratio (1.08) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.