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Finding the Fourth Proportional to 139.51, 209.42 and 81.80

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Solution

The fourth proportional to 139.51, 209.42 and 81.80 is: 122.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.51 : 209.42 = 81.80 : x
  2. Step 2: Convert to fraction form
    139.51/209.42 = 81.80/x
  3. Step 3: Cross multiply
    139.51x = 209.42 × 81.80
  4. Step 4: Simplify right side
    139.51x = 17,130.56
  5. Step 5: Solve for x
    x = 17,130.56/139.51
  6. Step 6: Final answer
    x = 122.79

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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.