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Finding the Fourth Proportional to 91.38, 126.21 and 81.66

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Solution

The fourth proportional to 91.38, 126.21 and 81.66 is: 112.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.38 : 126.21 = 81.66 : x
  2. Step 2: Convert to fraction form
    91.38/126.21 = 81.66/x
  3. Step 3: Cross multiply
    91.38x = 126.21 × 81.66
  4. Step 4: Simplify right side
    91.38x = 10,306.31
  5. Step 5: Solve for x
    x = 10,306.31/91.38
  6. Step 6: Final answer
    x = 112.79

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.