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Finding the Fourth Proportional to 399.60, 551.04 and 390.66

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Solution

The fourth proportional to 399.60, 551.04 and 390.66 is: 538.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    399.60 : 551.04 = 390.66 : x
  2. Step 2: Convert to fraction form
    399.60/551.04 = 390.66/x
  3. Step 3: Cross multiply
    399.60x = 551.04 × 390.66
  4. Step 4: Simplify right side
    399.60x = 215,269.29
  5. Step 5: Solve for x
    x = 215,269.29/399.60
  6. Step 6: Final answer
    x = 538.71

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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.