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Finding the Fourth Proportional to 420.31, 579.21 and 390.58

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Solution

The fourth proportional to 420.31, 579.21 and 390.58 is: 538.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.31 : 579.21 = 390.58 : x
  2. Step 2: Convert to fraction form
    420.31/579.21 = 390.58/x
  3. Step 3: Cross multiply
    420.31x = 579.21 × 390.58
  4. Step 4: Simplify right side
    420.31x = 226,231.75
  5. Step 5: Solve for x
    x = 226,231.75/420.31
  6. Step 6: Final answer
    x = 538.24

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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.