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Finding the Third Proportional to 390 and 661

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Solution

The third proportional to 390 and 661 is: 1,120.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    390 : 661 = 661 : x
  2. Step 2: Convert to fraction form
    390/661 = 661/x
  3. Step 3: Cross multiply
    390x = 661 × 661
  4. Step 4: Simplify right side
    390x = 436,921
  5. Step 5: Solve for x
    x = 436,921/390
  6. Step 6: Final answer
    x = 1,120.31

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Why These Related Problems?

These problems maintain the same ratio (1.69) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.