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Finding the Fourth Proportional to 139.31, 209.15 and 87.79

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Solution

The fourth proportional to 139.31, 209.15 and 87.79 is: 131.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.31 : 209.15 = 87.79 : x
  2. Step 2: Convert to fraction form
    139.31/209.15 = 87.79/x
  3. Step 3: Cross multiply
    139.31x = 209.15 × 87.79
  4. Step 4: Simplify right side
    139.31x = 18,361.28
  5. Step 5: Solve for x
    x = 18,361.28/139.31
  6. Step 6: Final answer
    x = 131.80

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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.