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Finding the Fourth Proportional to 420.78, 579.86 and 280.74

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Solution

The fourth proportional to 420.78, 579.86 and 280.74 is: 386.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.78 : 579.86 = 280.74 : x
  2. Step 2: Convert to fraction form
    420.78/579.86 = 280.74/x
  3. Step 3: Cross multiply
    420.78x = 579.86 × 280.74
  4. Step 4: Simplify right side
    420.78x = 162,789.90
  5. Step 5: Solve for x
    x = 162,789.90/420.78
  6. Step 6: Final answer
    x = 386.88

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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.