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Finding the Fourth Proportional to 139.21, 208.89 and 78.37

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Solution

The fourth proportional to 139.21, 208.89 and 78.37 is: 117.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.21 : 208.89 = 78.37 : x
  2. Step 2: Convert to fraction form
    139.21/208.89 = 78.37/x
  3. Step 3: Cross multiply
    139.21x = 208.89 × 78.37
  4. Step 4: Simplify right side
    139.21x = 16,370.71
  5. Step 5: Solve for x
    x = 16,370.71/139.21
  6. Step 6: Final answer
    x = 117.60

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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.