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Finding the Fourth Proportional to 842.20, 1,261.80 and 408.40

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Solution

The fourth proportional to 842.20, 1,261.80 and 408.40 is: 611.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    842.20 : 1,261.80 = 408.40 : x
  2. Step 2: Convert to fraction form
    842.20/1,261.80 = 408.40/x
  3. Step 3: Cross multiply
    842.20x = 1,261.80 × 408.40
  4. Step 4: Simplify right side
    842.20x = 515,319.12
  5. Step 5: Solve for x
    x = 515,319.12/842.20
  6. Step 6: Final answer
    x = 611.87

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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.