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Finding the Fourth Proportional to 420.75, 628.81 and 387.91

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Solution

The fourth proportional to 420.75, 628.81 and 387.91 is: 579.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.75 : 628.81 = 387.91 : x
  2. Step 2: Convert to fraction form
    420.75/628.81 = 387.91/x
  3. Step 3: Cross multiply
    420.75x = 628.81 × 387.91
  4. Step 4: Simplify right side
    420.75x = 243,921.69
  5. Step 5: Solve for x
    x = 243,921.69/420.75
  6. Step 6: Final answer
    x = 579.73

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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.