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Finding the Fourth Proportional to 645.20, 890.42 and 393.31

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Solution

The fourth proportional to 645.20, 890.42 and 393.31 is: 542.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    645.20 : 890.42 = 393.31 : x
  2. Step 2: Convert to fraction form
    645.20/890.42 = 393.31/x
  3. Step 3: Cross multiply
    645.20x = 890.42 × 393.31
  4. Step 4: Simplify right side
    645.20x = 350,211.09
  5. Step 5: Solve for x
    x = 350,211.09/645.20
  6. Step 6: Final answer
    x = 542.79

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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.