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Finding the Fourth Proportional to 139.47, 209.30 and 81.74

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Solution

The fourth proportional to 139.47, 209.30 and 81.74 is: 122.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.47 : 209.30 = 81.74 : x
  2. Step 2: Convert to fraction form
    139.47/209.30 = 81.74/x
  3. Step 3: Cross multiply
    139.47x = 209.30 × 81.74
  4. Step 4: Simplify right side
    139.47x = 17,108.18
  5. Step 5: Solve for x
    x = 17,108.18/139.47
  6. Step 6: Final answer
    x = 122.67

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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.