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Finding the Fourth Proportional to 781.28, 1,078.20 and 449.78

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Solution

The fourth proportional to 781.28, 1,078.20 and 449.78 is: 620.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.28 : 1,078.20 = 449.78 : x
  2. Step 2: Convert to fraction form
    781.28/1,078.20 = 449.78/x
  3. Step 3: Cross multiply
    781.28x = 1,078.20 × 449.78
  4. Step 4: Simplify right side
    781.28x = 484,952.80
  5. Step 5: Solve for x
    x = 484,952.80/781.28
  6. Step 6: Final answer
    x = 620.72

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.