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Finding the Fourth Proportional to 390.75, 539.60 and 287.79

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Solution

The fourth proportional to 390.75, 539.60 and 287.79 is: 397.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.75 : 539.60 = 287.79 : x
  2. Step 2: Convert to fraction form
    390.75/539.60 = 287.79/x
  3. Step 3: Cross multiply
    390.75x = 539.60 × 287.79
  4. Step 4: Simplify right side
    390.75x = 155,291.48
  5. Step 5: Solve for x
    x = 155,291.48/390.75
  6. Step 6: Final answer
    x = 397.42

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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.