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Finding the Third Proportional to 398 and 820

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Solution

The third proportional to 398 and 820 is: 1,689.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    398 : 820 = 820 : x
  2. Step 2: Convert to fraction form
    398/820 = 820/x
  3. Step 3: Cross multiply
    398x = 820 × 820
  4. Step 4: Simplify right side
    398x = 672,400
  5. Step 5: Solve for x
    x = 672,400/398
  6. Step 6: Final answer
    x = 1,689.45

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Why These Related Problems?

These problems maintain the same ratio (2.06) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.