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Finding the Fourth Proportional to 1,287.80, 1,780.62 and 1,123.78

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Solution

The fourth proportional to 1,287.80, 1,780.62 and 1,123.78 is: 1,553.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.80 : 1,780.62 = 1,123.78 : x
  2. Step 2: Convert to fraction form
    1,287.80/1,780.62 = 1,123.78/x
  3. Step 3: Cross multiply
    1,287.80x = 1,780.62 × 1,123.78
  4. Step 4: Simplify right side
    1,287.80x = 2,001,025.14
  5. Step 5: Solve for x
    x = 2,001,025.14/1,287.80
  6. Step 6: Final answer
    x = 1,553.83

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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.