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Finding the Third Proportional to 689 and 1,291

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Solution

The third proportional to 689 and 1,291 is: 2,418.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    689 : 1,291 = 1,291 : x
  2. Step 2: Convert to fraction form
    689/1,291 = 1,291/x
  3. Step 3: Cross multiply
    689x = 1,291 × 1,291
  4. Step 4: Simplify right side
    689x = 1,666,681
  5. Step 5: Solve for x
    x = 1,666,681/689
  6. Step 6: Final answer
    x = 2,418.99

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Why These Related Problems?

These problems maintain the same ratio (1.87) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.