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Finding the Fourth Proportional to 139.05, 208.44 and 78.21

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Solution

The fourth proportional to 139.05, 208.44 and 78.21 is: 117.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.05 : 208.44 = 78.21 : x
  2. Step 2: Convert to fraction form
    139.05/208.44 = 78.21/x
  3. Step 3: Cross multiply
    139.05x = 208.44 × 78.21
  4. Step 4: Simplify right side
    139.05x = 16,302.09
  5. Step 5: Solve for x
    x = 16,302.09/139.05
  6. Step 6: Final answer
    x = 117.24

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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.