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Finding the Fourth Proportional to 139.25, 208.89 and 78.40

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Solution

The fourth proportional to 139.25, 208.89 and 78.40 is: 117.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.25 : 208.89 = 78.40 : x
  2. Step 2: Convert to fraction form
    139.25/208.89 = 78.40/x
  3. Step 3: Cross multiply
    139.25x = 208.89 × 78.40
  4. Step 4: Simplify right side
    139.25x = 16,376.98
  5. Step 5: Solve for x
    x = 16,376.98/139.25
  6. Step 6: Final answer
    x = 117.61

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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.