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Finding the Fourth Proportional to 1,120.31, 1,680.47 and 389.90

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Solution

The fourth proportional to 1,120.31, 1,680.47 and 389.90 is: 584.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.31 : 1,680.47 = 389.90 : x
  2. Step 2: Convert to fraction form
    1,120.31/1,680.47 = 389.90/x
  3. Step 3: Cross multiply
    1,120.31x = 1,680.47 × 389.90
  4. Step 4: Simplify right side
    1,120.31x = 655,204.90
  5. Step 5: Solve for x
    x = 655,204.90/1,120.31
  6. Step 6: Final answer
    x = 584.85

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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.