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Finding the Fourth Proportional to 819.20, 1,227.70 and 428.39

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Solution

The fourth proportional to 819.20, 1,227.70 and 428.39 is: 642.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    819.20 : 1,227.70 = 428.39 : x
  2. Step 2: Convert to fraction form
    819.20/1,227.70 = 428.39/x
  3. Step 3: Cross multiply
    819.20x = 1,227.70 × 428.39
  4. Step 4: Simplify right side
    819.20x = 525,934.40
  5. Step 5: Solve for x
    x = 525,934.40/819.20
  6. Step 6: Final answer
    x = 642.01

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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.