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Finding the Fourth Proportional to 81.38, 121.81 and 45.20

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Solution

The fourth proportional to 81.38, 121.81 and 45.20 is: 67.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.38 : 121.81 = 45.20 : x
  2. Step 2: Convert to fraction form
    81.38/121.81 = 45.20/x
  3. Step 3: Cross multiply
    81.38x = 121.81 × 45.20
  4. Step 4: Simplify right side
    81.38x = 5,505.81
  5. Step 5: Solve for x
    x = 5,505.81/81.38
  6. Step 6: Final answer
    x = 67.66

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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.