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Finding the Third Proportional to 390 and 511

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Solution

The third proportional to 390 and 511 is: 669.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    390 : 511 = 511 : x
  2. Step 2: Convert to fraction form
    390/511 = 511/x
  3. Step 3: Cross multiply
    390x = 511 × 511
  4. Step 4: Simplify right side
    390x = 261,121
  5. Step 5: Solve for x
    x = 261,121/390
  6. Step 6: Final answer
    x = 669.54

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Why These Related Problems?

These problems maintain the same ratio (1.31) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.