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Finding the Third Proportional to 643.78 and 1,386.28

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Solution

The third proportional to 643.78 and 1,386.28 is: 2,985.14

Step by Step Solution

  1. Step 1: Write the proportion equation
    643.78 : 1,386.28 = 1,386.28 : x
  2. Step 2: Convert to fraction form
    643.78/1,386.28 = 1,386.28/x
  3. Step 3: Cross multiply
    643.78x = 1,386.28 × 1,386.28
  4. Step 4: Simplify right side
    643.78x = 1,921,775.70
  5. Step 5: Solve for x
    x = 1,921,775.70/643.78
  6. Step 6: Final answer
    x = 2,985.14

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Why These Related Problems?

These problems maintain the same ratio (2.15) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.