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Finding the Fourth Proportional to 685.20, 1,027.80 and 393.60

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Solution

The fourth proportional to 685.20, 1,027.80 and 393.60 is: 590.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.20 : 1,027.80 = 393.60 : x
  2. Step 2: Convert to fraction form
    685.20/1,027.80 = 393.60/x
  3. Step 3: Cross multiply
    685.20x = 1,027.80 × 393.60
  4. Step 4: Simplify right side
    685.20x = 404,542.08
  5. Step 5: Solve for x
    x = 404,542.08/685.20
  6. Step 6: Final answer
    x = 590.40

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.