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Finding the Fourth Proportional to 420.72, 580.38 and 289.80

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Solution

The fourth proportional to 420.72, 580.38 and 289.80 is: 399.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.72 : 580.38 = 289.80 : x
  2. Step 2: Convert to fraction form
    420.72/580.38 = 289.80/x
  3. Step 3: Cross multiply
    420.72x = 580.38 × 289.80
  4. Step 4: Simplify right side
    420.72x = 168,194.12
  5. Step 5: Solve for x
    x = 168,194.12/420.72
  6. Step 6: Final answer
    x = 399.78

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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.