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Finding the Fourth Proportional to 21,279.78, 31,919.76 and 7,428.78

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Solution

The fourth proportional to 21,279.78, 31,919.76 and 7,428.78 is: 11,143.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    21,279.78 : 31,919.76 = 7,428.78 : x
  2. Step 2: Convert to fraction form
    21,279.78/31,919.76 = 7,428.78/x
  3. Step 3: Cross multiply
    21,279.78x = 31,919.76 × 7,428.78
  4. Step 4: Simplify right side
    21,279.78x = 237,124,874.69
  5. Step 5: Solve for x
    x = 237,124,874.69/21,279.78
  6. Step 6: Final answer
    x = 11,143.20

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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.