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Finding the Fourth Proportional to 205.15, 307.76 and 81.78

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Solution

The fourth proportional to 205.15, 307.76 and 81.78 is: 122.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    205.15 : 307.76 = 81.78 : x
  2. Step 2: Convert to fraction form
    205.15/307.76 = 81.78/x
  3. Step 3: Cross multiply
    205.15x = 307.76 × 81.78
  4. Step 4: Simplify right side
    205.15x = 25,169.70
  5. Step 5: Solve for x
    x = 25,169.70/205.15
  6. Step 6: Final answer
    x = 122.69

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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.