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Finding the Fourth Proportional to 139.76, 209.64 and 78.80

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Solution

The fourth proportional to 139.76, 209.64 and 78.80 is: 118.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.76 : 209.64 = 78.80 : x
  2. Step 2: Convert to fraction form
    139.76/209.64 = 78.80/x
  3. Step 3: Cross multiply
    139.76x = 209.64 × 78.80
  4. Step 4: Simplify right side
    139.76x = 16,519.63
  5. Step 5: Solve for x
    x = 16,519.63/139.76
  6. Step 6: Final answer
    x = 118.20

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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.