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Finding the Fourth Proportional to 91.21, 136.21 and 81.13

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Solution

The fourth proportional to 91.21, 136.21 and 81.13 is: 121.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    91.21 : 136.21 = 81.13 : x
  2. Step 2: Convert to fraction form
    91.21/136.21 = 81.13/x
  3. Step 3: Cross multiply
    91.21x = 136.21 × 81.13
  4. Step 4: Simplify right side
    91.21x = 11,049.73
  5. Step 5: Solve for x
    x = 11,049.73/91.21
  6. Step 6: Final answer
    x = 121.15

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.