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Finding the Fourth Proportional to 139.72, 209.64 and 81.96

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Solution

The fourth proportional to 139.72, 209.64 and 81.96 is: 122.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.72 : 209.64 = 81.96 : x
  2. Step 2: Convert to fraction form
    139.72/209.64 = 81.96/x
  3. Step 3: Cross multiply
    139.72x = 209.64 × 81.96
  4. Step 4: Simplify right side
    139.72x = 17,182.09
  5. Step 5: Solve for x
    x = 17,182.09/139.72
  6. Step 6: Final answer
    x = 122.98

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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.