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Finding the Fourth Proportional to 139.50, 209.19 and 81.66

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Solution

The fourth proportional to 139.50, 209.19 and 81.66 is: 122.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.50 : 209.19 = 81.66 : x
  2. Step 2: Convert to fraction form
    139.50/209.19 = 81.66/x
  3. Step 3: Cross multiply
    139.50x = 209.19 × 81.66
  4. Step 4: Simplify right side
    139.50x = 17,082.46
  5. Step 5: Solve for x
    x = 17,082.46/139.50
  6. Step 6: Final answer
    x = 122.45

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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.