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Finding the Fourth Proportional to 138.12, 206.90 and 61

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Solution

The fourth proportional to 138.12, 206.90 and 61 is: 91.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.12 : 206.90 = 61 : x
  2. Step 2: Convert to fraction form
    138.12/206.90 = 61/x
  3. Step 3: Cross multiply
    138.12x = 206.90 × 61
  4. Step 4: Simplify right side
    138.12x = 12,620.90
  5. Step 5: Solve for x
    x = 12,620.90/138.12
  6. Step 6: Final answer
    x = 91.38

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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.