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Finding the Fourth Proportional to 421.20, 582.12 and 390.96

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Solution

The fourth proportional to 421.20, 582.12 and 390.96 is: 540.33

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.20 : 582.12 = 390.96 : x
  2. Step 2: Convert to fraction form
    421.20/582.12 = 390.96/x
  3. Step 3: Cross multiply
    421.20x = 582.12 × 390.96
  4. Step 4: Simplify right side
    421.20x = 227,585.64
  5. Step 5: Solve for x
    x = 227,585.64/421.20
  6. Step 6: Final answer
    x = 540.33

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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.