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Finding the Fourth Proportional to 211.38, 316.85 and 81.29

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Solution

The fourth proportional to 211.38, 316.85 and 81.29 is: 121.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.38 : 316.85 = 81.29 : x
  2. Step 2: Convert to fraction form
    211.38/316.85 = 81.29/x
  3. Step 3: Cross multiply
    211.38x = 316.85 × 81.29
  4. Step 4: Simplify right side
    211.38x = 25,755.34
  5. Step 5: Solve for x
    x = 25,755.34/211.38
  6. Step 6: Final answer
    x = 121.85

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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.