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Finding the Fourth Proportional to 139.88, 209.61 and 71.21

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Solution

The fourth proportional to 139.88, 209.61 and 71.21 is: 106.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.88 : 209.61 = 71.21 : x
  2. Step 2: Convert to fraction form
    139.88/209.61 = 71.21/x
  3. Step 3: Cross multiply
    139.88x = 209.61 × 71.21
  4. Step 4: Simplify right side
    139.88x = 14,926.33
  5. Step 5: Solve for x
    x = 14,926.33/139.88
  6. Step 6: Final answer
    x = 106.71

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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.