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Finding the Third Proportional to 687 and 1,389.75

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Solution

The third proportional to 687 and 1,389.75 is: 2,811.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    687 : 1,389.75 = 1,389.75 : x
  2. Step 2: Convert to fraction form
    687/1,389.75 = 1,389.75/x
  3. Step 3: Cross multiply
    687x = 1,389.75 × 1,389.75
  4. Step 4: Simplify right side
    687x = 1,931,405.06
  5. Step 5: Solve for x
    x = 1,931,405.06/687
  6. Step 6: Final answer
    x = 2,811.36

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Why These Related Problems?

These problems maintain the same ratio (2.02) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.