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Finding the Fourth Proportional to 390.56, 539.19 and 257.78

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Solution

The fourth proportional to 390.56, 539.19 and 257.78 is: 355.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.56 : 539.19 = 257.78 : x
  2. Step 2: Convert to fraction form
    390.56/539.19 = 257.78/x
  3. Step 3: Cross multiply
    390.56x = 539.19 × 257.78
  4. Step 4: Simplify right side
    390.56x = 138,993.75
  5. Step 5: Solve for x
    x = 138,993.75/390.56
  6. Step 6: Final answer
    x = 355.89

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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.