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Finding the Third Proportional to 312 and 687

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Solution

The third proportional to 312 and 687 is: 1,512.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    312 : 687 = 687 : x
  2. Step 2: Convert to fraction form
    312/687 = 687/x
  3. Step 3: Cross multiply
    312x = 687 × 687
  4. Step 4: Simplify right side
    312x = 471,969
  5. Step 5: Solve for x
    x = 471,969/312
  6. Step 6: Final answer
    x = 1,512.72

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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.