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Finding the Fourth Proportional to 1,120.78, 1,679.31 and 389.96

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Solution

The fourth proportional to 1,120.78, 1,679.31 and 389.96 is: 584.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.78 : 1,679.31 = 389.96 : x
  2. Step 2: Convert to fraction form
    1,120.78/1,679.31 = 389.96/x
  3. Step 3: Cross multiply
    1,120.78x = 1,679.31 × 389.96
  4. Step 4: Simplify right side
    1,120.78x = 654,863.73
  5. Step 5: Solve for x
    x = 654,863.73/1,120.78
  6. Step 6: Final answer
    x = 584.29

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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.