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Finding the Third Proportional to 391.50 and 645

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Solution

The third proportional to 391.50 and 645 is: 1,062.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    391.50 : 645 = 645 : x
  2. Step 2: Convert to fraction form
    391.50/645 = 645/x
  3. Step 3: Cross multiply
    391.50x = 645 × 645
  4. Step 4: Simplify right side
    391.50x = 416,025
  5. Step 5: Solve for x
    x = 416,025/391.50
  6. Step 6: Final answer
    x = 1,062.64

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Why These Related Problems?

These problems maintain the same ratio (1.65) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.