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Finding the Fourth Proportional to 20,980, 31,470 and 7,129.12

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Solution

The fourth proportional to 20,980, 31,470 and 7,129.12 is: 10,693.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    20,980 : 31,470 = 7,129.12 : x
  2. Step 2: Convert to fraction form
    20,980/31,470 = 7,129.12/x
  3. Step 3: Cross multiply
    20,980x = 31,470 × 7,129.12
  4. Step 4: Simplify right side
    20,980x = 224,353,406.40
  5. Step 5: Solve for x
    x = 224,353,406.40/20,980
  6. Step 6: Final answer
    x = 10,693.68

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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.