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Finding the Fourth Proportional to 139.29, 209 and 78.45

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Solution

The fourth proportional to 139.29, 209 and 78.45 is: 117.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.29 : 209 = 78.45 : x
  2. Step 2: Convert to fraction form
    139.29/209 = 78.45/x
  3. Step 3: Cross multiply
    139.29x = 209 × 78.45
  4. Step 4: Simplify right side
    139.29x = 16,396.05
  5. Step 5: Solve for x
    x = 16,396.05/139.29
  6. Step 6: Final answer
    x = 117.71

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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.