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Finding the Third Proportional to 391 and 640.50

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Solution

The third proportional to 391 and 640.50 is: 1,049.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    391 : 640.50 = 640.50 : x
  2. Step 2: Convert to fraction form
    391/640.50 = 640.50/x
  3. Step 3: Cross multiply
    391x = 640.50 × 640.50
  4. Step 4: Simplify right side
    391x = 410,240.25
  5. Step 5: Solve for x
    x = 410,240.25/391
  6. Step 6: Final answer
    x = 1,049.21

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Why These Related Problems?

These problems maintain the same ratio (1.64) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.