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Finding the Fourth Proportional to 139.43, 209.15 and 57.21

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Solution

The fourth proportional to 139.43, 209.15 and 57.21 is: 85.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.43 : 209.15 = 57.21 : x
  2. Step 2: Convert to fraction form
    139.43/209.15 = 57.21/x
  3. Step 3: Cross multiply
    139.43x = 209.15 × 57.21
  4. Step 4: Simplify right side
    139.43x = 11,965.47
  5. Step 5: Solve for x
    x = 11,965.47/139.43
  6. Step 6: Final answer
    x = 85.82

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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.