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Finding the Fourth Proportional to 81.25, 121.91 and 56.90

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Solution

The fourth proportional to 81.25, 121.91 and 56.90 is: 85.37

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.25 : 121.91 = 56.90 : x
  2. Step 2: Convert to fraction form
    81.25/121.91 = 56.90/x
  3. Step 3: Cross multiply
    81.25x = 121.91 × 56.90
  4. Step 4: Simplify right side
    81.25x = 6,936.70
  5. Step 5: Solve for x
    x = 6,936.70/81.25
  6. Step 6: Final answer
    x = 85.37

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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.