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Finding the Fourth Proportional to 139.55, 209.12 and 78.66

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Solution

The fourth proportional to 139.55, 209.12 and 78.66 is: 117.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.55 : 209.12 = 78.66 : x
  2. Step 2: Convert to fraction form
    139.55/209.12 = 78.66/x
  3. Step 3: Cross multiply
    139.55x = 209.12 × 78.66
  4. Step 4: Simplify right side
    139.55x = 16,448.99
  5. Step 5: Solve for x
    x = 16,448.99/139.55
  6. Step 6: Final answer
    x = 117.88

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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.