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Finding the Third Proportional to 399 and 720

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Solution

The third proportional to 399 and 720 is: 1,299.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    399 : 720 = 720 : x
  2. Step 2: Convert to fraction form
    399/720 = 720/x
  3. Step 3: Cross multiply
    399x = 720 × 720
  4. Step 4: Simplify right side
    399x = 518,400
  5. Step 5: Solve for x
    x = 518,400/399
  6. Step 6: Final answer
    x = 1,299.25

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Why These Related Problems?

These problems maintain the same ratio (1.80) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.