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Finding the Fourth Proportional to 206.80, 309.70 and 138.12

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Solution

The fourth proportional to 206.80, 309.70 and 138.12 is: 206.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    206.80 : 309.70 = 138.12 : x
  2. Step 2: Convert to fraction form
    206.80/309.70 = 138.12/x
  3. Step 3: Cross multiply
    206.80x = 309.70 × 138.12
  4. Step 4: Simplify right side
    206.80x = 42,775.76
  5. Step 5: Solve for x
    x = 42,775.76/206.80
  6. Step 6: Final answer
    x = 206.85

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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.