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Finding the Third Proportional to 643.78 and 691.03

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Solution

The third proportional to 643.78 and 691.03 is: 741.75

Step by Step Solution

  1. Step 1: Write the proportion equation
    643.78 : 691.03 = 691.03 : x
  2. Step 2: Convert to fraction form
    643.78/691.03 = 691.03/x
  3. Step 3: Cross multiply
    643.78x = 691.03 × 691.03
  4. Step 4: Simplify right side
    643.78x = 477,524.19
  5. Step 5: Solve for x
    x = 477,524.19/643.78
  6. Step 6: Final answer
    x = 741.75

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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.