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Finding the Fourth Proportional to 81.42, 121.86 and 57.39

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Solution

The fourth proportional to 81.42, 121.86 and 57.39 is: 85.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.42 : 121.86 = 57.39 : x
  2. Step 2: Convert to fraction form
    81.42/121.86 = 57.39/x
  3. Step 3: Cross multiply
    81.42x = 121.86 × 57.39
  4. Step 4: Simplify right side
    81.42x = 6,993.55
  5. Step 5: Solve for x
    x = 6,993.55/81.42
  6. Step 6: Final answer
    x = 85.89

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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.