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Finding the Fourth Proportional to 1,919.78, 2,879.70 and 687.20

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Solution

The fourth proportional to 1,919.78, 2,879.70 and 687.20 is: 1,030.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,919.78 : 2,879.70 = 687.20 : x
  2. Step 2: Convert to fraction form
    1,919.78/2,879.70 = 687.20/x
  3. Step 3: Cross multiply
    1,919.78x = 2,879.70 × 687.20
  4. Step 4: Simplify right side
    1,919.78x = 1,978,929.84
  5. Step 5: Solve for x
    x = 1,978,929.84/1,919.78
  6. Step 6: Final answer
    x = 1,030.81

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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.