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Finding the Fourth Proportional to 819.90, 1,229.70 and 511.20

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Solution

The fourth proportional to 819.90, 1,229.70 and 511.20 is: 766.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    819.90 : 1,229.70 = 511.20 : x
  2. Step 2: Convert to fraction form
    819.90/1,229.70 = 511.20/x
  3. Step 3: Cross multiply
    819.90x = 1,229.70 × 511.20
  4. Step 4: Simplify right side
    819.90x = 628,622.64
  5. Step 5: Solve for x
    x = 628,622.64/819.90
  6. Step 6: Final answer
    x = 766.71

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.