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Finding the Fourth Proportional to 420.39, 580.16 and 391.23

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Solution

The fourth proportional to 420.39, 580.16 and 391.23 is: 539.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.39 : 580.16 = 391.23 : x
  2. Step 2: Convert to fraction form
    420.39/580.16 = 391.23/x
  3. Step 3: Cross multiply
    420.39x = 580.16 × 391.23
  4. Step 4: Simplify right side
    420.39x = 226,976.97
  5. Step 5: Solve for x
    x = 226,976.97/420.39
  6. Step 6: Final answer
    x = 539.92

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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.