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Finding the Third Proportional to 390 and 406.50

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Solution

The third proportional to 390 and 406.50 is: 423.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    390 : 406.50 = 406.50 : x
  2. Step 2: Convert to fraction form
    390/406.50 = 406.50/x
  3. Step 3: Cross multiply
    390x = 406.50 × 406.50
  4. Step 4: Simplify right side
    390x = 165,242.25
  5. Step 5: Solve for x
    x = 165,242.25/390
  6. Step 6: Final answer
    x = 423.70

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Why These Related Problems?

These problems maintain the same ratio (1.04) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.