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Finding the Fourth Proportional to 206.80, 309.90 and 91.15

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Solution

The fourth proportional to 206.80, 309.90 and 91.15 is: 136.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    206.80 : 309.90 = 91.15 : x
  2. Step 2: Convert to fraction form
    206.80/309.90 = 91.15/x
  3. Step 3: Cross multiply
    206.80x = 309.90 × 91.15
  4. Step 4: Simplify right side
    206.80x = 28,247.39
  5. Step 5: Solve for x
    x = 28,247.39/206.80
  6. Step 6: Final answer
    x = 136.59

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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.