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Finding the Fourth Proportional to 139.15, 208.55 and 66.86

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Solution

The fourth proportional to 139.15, 208.55 and 66.86 is: 100.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.15 : 208.55 = 66.86 : x
  2. Step 2: Convert to fraction form
    139.15/208.55 = 66.86/x
  3. Step 3: Cross multiply
    139.15x = 208.55 × 66.86
  4. Step 4: Simplify right side
    139.15x = 13,942.78
  5. Step 5: Solve for x
    x = 13,942.78/139.15
  6. Step 6: Final answer
    x = 100.20

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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.