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Finding the Fourth Proportional to 1,279.20, 1,765.20 and 813

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Solution

The fourth proportional to 1,279.20, 1,765.20 and 813 is: 1,121.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,279.20 : 1,765.20 = 813 : x
  2. Step 2: Convert to fraction form
    1,279.20/1,765.20 = 813/x
  3. Step 3: Cross multiply
    1,279.20x = 1,765.20 × 813
  4. Step 4: Simplify right side
    1,279.20x = 1,435,107.60
  5. Step 5: Solve for x
    x = 1,435,107.60/1,279.20
  6. Step 6: Final answer
    x = 1,121.88

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.