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Finding the Third Proportional to 640.72 and 989.92

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Solution

The third proportional to 640.72 and 989.92 is: 1,529.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    640.72 : 989.92 = 989.92 : x
  2. Step 2: Convert to fraction form
    640.72/989.92 = 989.92/x
  3. Step 3: Cross multiply
    640.72x = 989.92 × 989.92
  4. Step 4: Simplify right side
    640.72x = 979,934.68
  5. Step 5: Solve for x
    x = 979,934.68/640.72
  6. Step 6: Final answer
    x = 1,529.42

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Why These Related Problems?

These problems maintain the same ratio (1.55) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.