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Finding the Third Proportional to 391 and 860

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Solution

The third proportional to 391 and 860 is: 1,891.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    391 : 860 = 860 : x
  2. Step 2: Convert to fraction form
    391/860 = 860/x
  3. Step 3: Cross multiply
    391x = 860 × 860
  4. Step 4: Simplify right side
    391x = 739,600
  5. Step 5: Solve for x
    x = 739,600/391
  6. Step 6: Final answer
    x = 1,891.56

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Why These Related Problems?

These problems maintain the same ratio (2.20) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.