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Finding the Fourth Proportional to 211.97, 317.90 and 81.91

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Solution

The fourth proportional to 211.97, 317.90 and 81.91 is: 122.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.97 : 317.90 = 81.91 : x
  2. Step 2: Convert to fraction form
    211.97/317.90 = 81.91/x
  3. Step 3: Cross multiply
    211.97x = 317.90 × 81.91
  4. Step 4: Simplify right side
    211.97x = 26,039.56
  5. Step 5: Solve for x
    x = 26,039.56/211.97
  6. Step 6: Final answer
    x = 122.85

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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.