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Finding the Fourth Proportional to 81.35, 121.89 and 57.19

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Solution

The fourth proportional to 81.35, 121.89 and 57.19 is: 85.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.35 : 121.89 = 57.19 : x
  2. Step 2: Convert to fraction form
    81.35/121.89 = 57.19/x
  3. Step 3: Cross multiply
    81.35x = 121.89 × 57.19
  4. Step 4: Simplify right side
    81.35x = 6,970.80
  5. Step 5: Solve for x
    x = 6,970.80/81.35
  6. Step 6: Final answer
    x = 85.69

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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.