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Finding the Fourth Proportional to 20,979, 31,473.36 and 7,128

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Solution

The fourth proportional to 20,979, 31,473.36 and 7,128 is: 10,693.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    20,979 : 31,473.36 = 7,128 : x
  2. Step 2: Convert to fraction form
    20,979/31,473.36 = 7,128/x
  3. Step 3: Cross multiply
    20,979x = 31,473.36 × 7,128
  4. Step 4: Simplify right side
    20,979x = 224,342,110.08
  5. Step 5: Solve for x
    x = 224,342,110.08/20,979
  6. Step 6: Final answer
    x = 10,693.65

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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.