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Finding the Third Proportional to 390 and 644.25

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Solution

The third proportional to 390 and 644.25 is: 1,064.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    390 : 644.25 = 644.25 : x
  2. Step 2: Convert to fraction form
    390/644.25 = 644.25/x
  3. Step 3: Cross multiply
    390x = 644.25 × 644.25
  4. Step 4: Simplify right side
    390x = 415,058.06
  5. Step 5: Solve for x
    x = 415,058.06/390
  6. Step 6: Final answer
    x = 1,064.25

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Why These Related Problems?

These problems maintain the same ratio (1.65) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.