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Finding the Fourth Proportional to 139.57, 209.21 and 90.76

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Solution

The fourth proportional to 139.57, 209.21 and 90.76 is: 136.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    139.57 : 209.21 = 90.76 : x
  2. Step 2: Convert to fraction form
    139.57/209.21 = 90.76/x
  3. Step 3: Cross multiply
    139.57x = 209.21 × 90.76
  4. Step 4: Simplify right side
    139.57x = 18,987.90
  5. Step 5: Solve for x
    x = 18,987.90/139.57
  6. Step 6: Final answer
    x = 136.05

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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.