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Finding the Fourth Proportional to 20,991, 31,491.36 and 7,140

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Solution

The fourth proportional to 20,991, 31,491.36 and 7,140 is: 10,711.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    20,991 : 31,491.36 = 7,140 : x
  2. Step 2: Convert to fraction form
    20,991/31,491.36 = 7,140/x
  3. Step 3: Cross multiply
    20,991x = 31,491.36 × 7,140
  4. Step 4: Simplify right side
    20,991x = 224,848,310.40
  5. Step 5: Solve for x
    x = 224,848,310.40/20,991
  6. Step 6: Final answer
    x = 10,711.65

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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.