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Finding the Fourth Proportional to 81.21, 121.85 and 37.90

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Solution

The fourth proportional to 81.21, 121.85 and 37.90 is: 56.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.21 : 121.85 = 37.90 : x
  2. Step 2: Convert to fraction form
    81.21/121.85 = 37.90/x
  3. Step 3: Cross multiply
    81.21x = 121.85 × 37.90
  4. Step 4: Simplify right side
    81.21x = 4,617.32
  5. Step 5: Solve for x
    x = 4,617.32/81.21
  6. Step 6: Final answer
    x = 56.86

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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.