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Finding the Fourth Proportional to 1,120.70, 1,679.90 and 389.87

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Solution

The fourth proportional to 1,120.70, 1,679.90 and 389.87 is: 584.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.70 : 1,679.90 = 389.87 : x
  2. Step 2: Convert to fraction form
    1,120.70/1,679.90 = 389.87/x
  3. Step 3: Cross multiply
    1,120.70x = 1,679.90 × 389.87
  4. Step 4: Simplify right side
    1,120.70x = 654,944.86
  5. Step 5: Solve for x
    x = 654,944.86/1,120.70
  6. Step 6: Final answer
    x = 584.41

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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.