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Finding the Fourth Proportional to 420.20, 578.50 and 390.76

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Solution

The fourth proportional to 420.20, 578.50 and 390.76 is: 537.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.20 : 578.50 = 390.76 : x
  2. Step 2: Convert to fraction form
    420.20/578.50 = 390.76/x
  3. Step 3: Cross multiply
    420.20x = 578.50 × 390.76
  4. Step 4: Simplify right side
    420.20x = 226,054.66
  5. Step 5: Solve for x
    x = 226,054.66/420.20
  6. Step 6: Final answer
    x = 537.97

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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.