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Finding the Fourth Proportional to 399.28, 551.31 and 392.90

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Solution

The fourth proportional to 399.28, 551.31 and 392.90 is: 542.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    399.28 : 551.31 = 392.90 : x
  2. Step 2: Convert to fraction form
    399.28/551.31 = 392.90/x
  3. Step 3: Cross multiply
    399.28x = 551.31 × 392.90
  4. Step 4: Simplify right side
    399.28x = 216,608.57
  5. Step 5: Solve for x
    x = 216,608.57/399.28
  6. Step 6: Final answer
    x = 542.50

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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.