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Finding the Fourth Proportional to 431.39, 644.42 and 387.99

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Solution

The fourth proportional to 431.39, 644.42 and 387.99 is: 579.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.39 : 644.42 = 387.99 : x
  2. Step 2: Convert to fraction form
    431.39/644.42 = 387.99/x
  3. Step 3: Cross multiply
    431.39x = 644.42 × 387.99
  4. Step 4: Simplify right side
    431.39x = 250,029.49
  5. Step 5: Solve for x
    x = 250,029.49/431.39
  6. Step 6: Final answer
    x = 579.59

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.