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Finding the Fourth Proportional to 261.78, 391.76 and 221.09

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Solution

The fourth proportional to 261.78, 391.76 and 221.09 is: 330.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.78 : 391.76 = 221.09 : x
  2. Step 2: Convert to fraction form
    261.78/391.76 = 221.09/x
  3. Step 3: Cross multiply
    261.78x = 391.76 × 221.09
  4. Step 4: Simplify right side
    261.78x = 86,611.15
  5. Step 5: Solve for x
    x = 86,611.15/261.78
  6. Step 6: Final answer
    x = 330.85

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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.